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\n\n {/* 可选：显示错误详情（生产环境可隐藏） */}\n {process.env.NODE_ENV === \"development\" && (\n

错误详情

\n {this.state.error?.message}\n
\n {this.state.errorInfo?.componentStack}\n

\n )}\n\n

\n \n \n

\n );\n }\n\n // 如果没有错误，渲染子组件\n return this.props.children;\n }\n}\n\nexport default ErrorBoundary;\n```\n\n2. **全局应用**\n\n - 在应用入口（App.jsx）用 ErrorBoundary 包裹整个应用，确保所有子组件的错误都能被捕获\n - 错误边界会自动捕获其内部所有组件（包括嵌套组件）的渲染错误、生命周期错误等\n\n```jsx\nimport React from \"react\";\nimport ErrorBoundary from \"./ErrorBoundary\";\nimport Router from \"./Router\"; // 你的路由组件\nimport GlobalStyle from \"./GlobalStyle\"; // 全局样式\n\nfunction App() {\n return (\n // 用错误边界包裹整个应用\n \n \n \n \n );\n}\n\nexport default App;\n```\n\n### 注意事项\n\n- 错误边界**不能捕获以下错误**：\n\n - 事件处理函数中的错误（需手动 try/catch）\n - 异步代码中的错误（如 setTimeout、Promise）\n - 错误边界自身的错误\n - 服务端渲染的错误\n\n- 对于异步错误（如 API 请求失败），需要额外在代码中处理（如 try/catch 或状态管理）\n\n- 可以根据需要扩展错误边界，例如：\n - 增加错误分类显示不同提示\n - 实现自动重试逻辑\n - 集成错误监控工具（如 Sentry）\n\n通过这种方式，你的 React 应用就能拥有一个全局的崩溃处理机制，在发生错误时给用户友好的提示，而不是白屏或控制台报错。\n","reactions",{"_58":179,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/1136/reactions","total_count","+1","-1","laugh","hooray","confused","heart","rocket","eyes","timeline_url","https://api.github.com/repos/pro-collection/interview-question/issues/1136/timeline","performed_via_github_app","state_reason","score",1,{"_58":196,"_60":61,"_62":197,"_64":198,"_66":199,"_68":200,"_70":201,"_72":202,"_74":203,"_76":204,"_78":205,"_111":206,"_131":132,"_133":24,"_134":-5,"_135":215,"_137":216,"_159":194,"_153":229,"_155":230,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":231,"_169":232,"_175":233,"_177":234,"_189":236,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/1066","https://api.github.com/repos/pro-collection/interview-question/issues/1066/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/1066/comments","https://api.github.com/repos/pro-collection/interview-question/issues/1066/events","https://github.com/pro-collection/interview-question/issues/1066",2683321083,"I_kwDOJGDC6c6f8Dr7",1066,"Object.defineProperty 是否可以监听拦截数组变化【热度: 144】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[207,214],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},5232521368,"LA_kwDOJGDC6c8AAAABN-HwmA","https://api.github.com/repos/pro-collection/interview-question/labels/JavaScript","JavaScript","A4D8FB","JavaScript 语法部分",{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":225,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},"https://api.github.com/repos/pro-collection/interview-question/milestones/3","https://github.com/pro-collection/interview-question/milestone/3","https://api.github.com/repos/pro-collection/interview-question/milestones/3/labels",9124547,"MI_kwDOJGDC6c4AizrD",3,"高","高级别面试问题",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},454,"2023-03-06T15:00:27Z","2025-09-07T06:21:17Z","2024-11-22T14:08:52Z","2025-02-27T10:34:11Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：Object.defineProperty 监听数组变化\n\n1. **基本原理与部分可行性**\n - `Object.defineProperty`可以用于监听和拦截数组的某些变化，但不是原生地对所有数组操作都能很好地监听。\n - 数组在 JavaScript 中是特殊的对象，其索引可以看作是对象属性。理论上，我们可以使用`Object.defineProperty`为数组的每个索引（属性）定义属性描述符，以此来尝试监听数组元素的读取和设置操作。\n - 例如，对于一个简单的数组元素设置操作，可以这样定义：\n ```javascript\n let arr = [1, 2, 3];\n Object.defineProperty(arr, \"0\", {\n get: function () {\n console.log(\"读取索引为0的元素\");\n return arr[0];\n },\n set: function (value) {\n console.log(\"设置索引为0的元素\");\n arr[0] = value;\n },\n });\n ```\n - 当通过`arr[0]`读取或设置元素时，相应的`get`和`set`函数会被触发，从而实现对这个特定索引元素的变化监听。\n2. **局限性**\n\n - **无法自动监听所有元素**：这种方式需要为每个要监听的索引单独使用`Object.defineProperty`进行定义。如果数组长度是动态变化的，或者要监听整个数组，这种逐个定义的方式就非常繁琐且不实用。例如，对于一个有很多元素的数组或者长度会不断变化的数组，几乎不可能预先为每个可能的索引都定义属性描述符。\n - **无法直接监听数组方法**：它不能直接监听数组的方法（如`push`、`pop`、`shift`、`unshift`、`splice`等）引起的变化。这些方法会改变数组的状态，但不会触发通过`Object.defineProperty`为数组元素定义的`get`和`set`操作。比如，当使用`push`方法添加元素到数组时，不会自动触发之前为数组元素定义的`set`操作来监听这个新元素的添加。\n\n3. **解决方案 - 重写数组方法实现全面监听**\n\n以下是使用`Object.defineProperty`来实现监听数组部分常见操作（如修改元素、添加元素、删除元素等）的基本思路和示例代码：\n\n**3.1. 整体思路**\n\n要使用`Object.defineProperty`监听数组，主要思路是对数组的原型方法进行重定义，在这些重定义的方法内部，通过`Object.defineProperty`来设置属性描述符，使得在执行这些操作时能够触发自定义的监听函数，从而实现对数组变化的监听。\n\n**3.2. 具体步骤及示例代码**\n\n**（1）创建一个继承自原生数组的新类**\n\n首先，创建一个新的类，让它继承自原生数组，以便后续可以在这个新类上添加自定义的监听逻辑。\n\n```javascript\nfunction ObservableArray() {\n // 调用原生数组构造函数，确保可以像正常数组一样使用\n Array.apply(this, arguments);\n}\nObservableArray.prototype = Object.create(Array.prototype);\nObservableArray.prototype.constructor = ObservableArray;\n```\n\n**（2）重定义数组的部分原型方法**\n\n接下来，重定义数组的一些常见操作的原型方法，比如`push`、`pop`、`shift`、`unshift`、`splice`等，在这些重定义的方法内部添加监听逻辑。\n\n以`push`方法为例：\n\n```javascript\nObservableArray.prototype.push = function () {\n // 保存当前数组长度，用于后续判断添加了几个元素\n var previousLength = this.length;\n\n // 调用原生数组的push方法，执行实际的添加操作\n var result = Array.prototype.push.apply(this, arguments);\n\n // 遍历新添加的元素，为每个元素设置属性描述符以实现监听\n for (var i = previousLength; i < this.length; i++) {\n (function (index) {\n Object.defineProperty(this, index, {\n enumerable: true,\n configurable: true,\n get: function () {\n console.log(\"正在读取索引为\" + index + \"的元素\");\n return this[index];\n },\n set: function (value) {\n console.log(\"正在设置索引为\" + index + \"的元素为\" + value);\n this[index] = value;\n },\n });\n }).call(this, i);\n }\n\n console.log(\"执行了push操作，添加了\" + (this.length - previousLength) + \"个元素\");\n\n return result;\n};\n```\n\n在上述`push`方法的重定义中：\n\n- 首先调用原生数组的`push`方法来执行实际的添加元素操作，并保存添加前的数组长度。\n- 然后，通过循环为新添加的每个元素使用`Object.defineProperty`设置属性描述符。在`get`方法中，当读取该元素时会打印相应信息；在`set`方法中，当设置该元素时也会打印相应信息。\n- 最后，打印出执行`push`操作添加的元素个数。\n\n类似地，可以重定义其他如`pop`、`shift`、`unshift`、`splice`等方法，以下是`pop`方法的重定义示例：\n\n```javascript\nObservableArray.prototype.pop = function () {\n var result = Array.prototype.pop.apply(this, arguments);\n\n if (this.length >= 0) {\n Object.defineProperty(this, this.length, {\n enumerable: true,\n configurable: true,\n get: function () {\n console.log(\"正在读取最后一个元素\");\n return this[this.length];\n },\n set: function (value) {\n console.log(\"正在设置最后一个元素为\" + value);\n this[this.length] = value;\n },\n });\n }\n\n console.log(\"执行了pop操作\");\n\n return result;\n};\n```\n\n**3.3. 使用示例**\n\n创建`ObservableArray`的实例并进行操作来测试监听效果：\n\n```javascript\nvar myArray = new ObservableArray(1, 2, 3);\n\nmyArray.push(4, 5);\nvar poppedElement = myArray.pop();\nmyArray[0] = 10;\n```\n\n在上述示例中：\n\n- 首先创建了一个`ObservableArray`实例`myArray`并初始化为`[1, 2, 3]`。\n- 然后执行`myArray.push(4, 5)`，此时会触发重定义的`push`方法，添加元素的同时会为新添加的元素设置监听逻辑，并且会打印出相关操作信息。\n- 接着执行`myArray.pop()`，触发重定义的`pop`方法，执行弹出操作并设置对最后一个元素的监听逻辑，同时打印出相关操作信息。\n- 最后执行`myArray[0] = 10`，由于之前为数组元素设置了监听逻辑（在`push`方法中对新添加元素设置了监听），所以会触发相应的`set`逻辑，打印出相关信息。\n",{"_58":235,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/1066/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/1066/timeline",{"_58":238,"_60":61,"_62":239,"_64":240,"_66":241,"_68":242,"_70":243,"_72":244,"_74":245,"_76":246,"_78":247,"_111":248,"_131":132,"_133":24,"_134":-5,"_135":251,"_137":252,"_159":152,"_153":254,"_155":255,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":256,"_169":257,"_175":258,"_177":259,"_189":261,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/1022","https://api.github.com/repos/pro-collection/interview-question/issues/1022/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/1022/comments","https://api.github.com/repos/pro-collection/interview-question/issues/1022/events","https://github.com/pro-collection/interview-question/issues/1022",2615602633,"I_kwDOJGDC6c6b5u3J",1022,"闭包有哪些使用场景，请举例【热度: 679】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[249,250],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":253,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-10-26T06:43:59Z","2024-10-26T06:56:04Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：闭包使用场景\n\n闭包在 JavaScript 中有很多实用的使用场景，以下是一些主要的场景：\n\n**一、数据隐藏和封装**\n\n1. 保护变量：\n\n - 闭包可以创建一个私有作用域，将变量封装在函数内部，防止外部直接访问和修改。只有通过特定的函数接口才能访问和操作这些变量。\n - 例如：\n\n ```javascript\n function createCounter() {\n let count = 0;\n return {\n increment() {\n count++;\n },\n getCount() {\n return count;\n },\n };\n }\n\n const counter = createCounter();\n counter.increment();\n console.log(counter.getCount()); // 1\n ```\n\n - 在这个例子中，`count`变量被封装在`createCounter`函数内部，外部无法直接访问，只能通过返回的对象上的方法来操作`count`。\n\n2. 模拟私有方法：\n\n - 在面向对象编程中，可以使用闭包来模拟私有方法。私有方法只能在对象内部被访问，外部无法直接调用。\n - 例如：\n\n ```javascript\n const myObject = (function () {\n let privateVariable = 0;\n\n function privateMethod() {\n privateVariable++;\n console.log(privateVariable);\n }\n\n return {\n publicMethod() {\n privateMethod();\n },\n };\n })();\n\n myObject.publicMethod(); // 1\n ```\n\n - 在这个例子中，`privateMethod`和`privateVariable`只能在内部函数中被访问，外部通过调用`publicMethod`间接访问了私有方法。\n\n**二、函数柯里化（Currying）**\n\n1. 逐步参数化：\n\n - 闭包可以用于实现函数柯里化，将一个多参数的函数转换为一系列单参数的函数。每次调用只接受一部分参数，并返回一个新的函数，直到所有参数都被提供。\n - 例如：\n\n ```javascript\n function add(a) {\n return function (b) {\n return function (c) {\n return a + b + c;\n };\n };\n }\n\n const addFiveAndSixAndSeven = add(5)(6)(7);\n console.log(addFiveAndSixAndSeven); // 18\n ```\n\n - 在这个例子中，`add`函数通过闭包逐步接受参数，最后返回一个计算结果。\n\n2. 灵活的参数传递：\n - 函数柯里化可以使函数的参数传递更加灵活，特别是在需要部分应用参数或者延迟参数传递的情况下。\n - 例如，可以先创建一个部分应用参数的函数，然后在需要的时候再传递剩余的参数。\n\n**三、回调函数和事件处理**\n\n1. 保存外部环境：\n\n - 在异步编程或者事件处理中，闭包可以保存外部函数的变量和状态，使得回调函数能够访问这些信息。\n - 例如：\n\n ```javascript\n function setTimeoutWithMessage(message) {\n setTimeout(function () {\n console.log(message);\n }, 1000);\n }\n\n setTimeoutWithMessage(\"Hello after 1 second!\");\n ```\n\n - 在这个例子中，回调函数内部的`message`变量是通过闭包从外部函数中获取的，即使外部函数已经执行完毕，回调函数仍然能够访问到这个变量。\n\n2. 事件处理程序：\n - 在 DOM 事件处理中，闭包可以用于保存与事件相关的状态和数据。\n - 例如：\n ```html\n \n \n ```\n - 在这个例子中，事件处理程序内部的`buttonText`变量是通过闭包从外部环境中获取的，每次点击按钮时，都能正确地打印出按钮的文本内容。\n\n**四、记忆化（Memoization）**\n\n1. 缓存计算结果：\n\n - 闭包可以用于实现记忆化，将函数的计算结果缓存起来，避免重复计算。如果相同的参数再次被传入，直接返回缓存的结果，而不是重新计算。\n - 例如：\n\n ```javascript\n function memoizedAdd() {\n let cache = {};\n return function (a, b) {\n const key = `${a},${b}`;\n if (cache[key]) {\n return cache[key];\n } else {\n const result = a + b;\n cache[key] = result;\n return result;\n }\n };\n }\n\n const memoizedAddFunction = memoizedAdd();\n console.log(memoizedAddFunction(2, 3)); // 5\n console.log(memoizedAddFunction(2, 3)); // 5（直接从缓存中获取结果）\n ```\n\n - 在这个例子中，`memoizedAdd`函数内部的`cache`对象用于缓存计算结果，通过闭包保存了这个缓存对象，使得每次调用函数时都能访问到它。\n\n2. 提高性能：\n - 对于计算复杂或者频繁调用的函数，记忆化可以显著提高性能，减少不必要的计算。\n",{"_58":260,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/1022/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/1022/timeline",{"_58":263,"_60":61,"_62":264,"_64":265,"_66":266,"_68":267,"_70":268,"_72":269,"_74":270,"_76":271,"_78":272,"_111":273,"_131":132,"_133":24,"_134":-5,"_135":276,"_137":277,"_159":194,"_153":279,"_155":280,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":281,"_169":282,"_175":283,"_177":284,"_189":286,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/983","https://api.github.com/repos/pro-collection/interview-question/issues/983/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/983/comments","https://api.github.com/repos/pro-collection/interview-question/issues/983/events","https://github.com/pro-collection/interview-question/issues/983",2583177466,"I_kwDOJGDC6c6Z-Cj6",983,"[React] 在 setState 时发生了什么【热度: 169】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[274,275],{"_70":114,"_72":115,"_58":116,"_117":118,"_119":120,"_121":24,"_122":123},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":278,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-10-12T15:29:46Z","2024-12-06T04:08:00Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：React setState 过程\n\n在 React 中，当调用`setState`时，会发生以下一系列事情：\n\n**一、触发状态更新**\n\n1. **调用 setState 方法**：\n - 当在 React 组件中调用`setState`方法时，React 会将这个状态更新请求排队。这意味着 React 不会立即更新组件的状态，而是将这个更新请求添加到一个队列中，等待合适的时机进行处理。\n - 例如：\n ```javascript\n this.setState({ count: this.state.count + 1 });\n ```\n - 在这个例子中，调用`setState`方法来增加`count`状态的值。\n\n**二、合并状态**\n\n1. **状态合并**：\n\n - 如果多次调用`setState`方法，React 会将这些状态更新请求合并在一起。这意味着 React 不会立即应用每个状态更新请求，而是会将它们合并成一个单一的状态更新。\n - 例如，如果在一个事件处理函数中多次调用`setState`方法：\n\n ```javascript\n handleClick() {\n this.setState({ count: this.state.count + 1 });\n this.setState({ count: this.state.count + 1 });\n }\n ```\n\n - React 不会立即将`count`的值增加两次，而是会将这两个状态更新请求合并成一个，最终只将`count`的值增加一次。\n\n2. **浅合并对象状态**：\n - 如果`setState`方法的参数是一个对象，React 会进行浅合并。这意味着如果状态是一个对象，并且只更新了其中的一部分属性，React 会将新的属性值合并到旧的状态对象中，而不会替换整个状态对象。\n - 例如：\n ```javascript\n this.setState({ user: { name: \"New Name\" } });\n ```\n - 如果原来的状态是`{ user: { name: 'Old Name', age: 30 } }`，那么调用`setState`方法后，新的状态将是`{ user: { name: 'New Name', age: 30 } }`。React 只会更新`user`对象的`name`属性，而不会影响`age`属性。\n\n**三、触发重新渲染**\n\n1. **协调阶段**：\n\n - 在合适的时机，React 会开始处理状态更新请求队列。React 会进入一个称为协调阶段的过程，在这个阶段，React 会比较组件的当前状态和新的状态，确定哪些组件需要重新渲染。\n - React 会使用一种称为虚拟 DOM 的技术来比较新旧状态，并确定最小化的更新操作，以提高性能。\n\n2. **重新渲染组件**：\n - 如果 React 确定某个组件的状态发生了变化，并且需要重新渲染，它会调用该组件的`render`方法来生成新的虚拟 DOM。然后，React 会将新的虚拟 DOM 与旧的虚拟 DOM 进行比较，确定需要进行哪些实际的 DOM 操作来更新页面。\n - 例如，如果一个组件的状态发生了变化，React 会调用该组件的`render`方法，生成新的虚拟 DOM，并将其与旧的虚拟 DOM 进行比较。如果有差异，React 会更新实际的 DOM，以反映新的状态。\n\n**四、异步执行**\n\n1. **异步更新状态**：\n\n - 在 React 中，`setState`方法通常是异步执行的。这意味着在调用`setState`方法后，不能立即依赖新的状态值。\n - 例如：\n\n ```javascript\n this.setState({ count: this.state.count + 1 });\n console.log(this.state.count);\n ```\n\n - 在这个例子中，`console.log`语句可能不会输出更新后的`count`值，因为`setState`方法是异步执行的，状态更新可能还没有完成。\n\n2. **使用回调函数**：\n - 如果需要在状态更新完成后执行一些操作，可以在`setState`方法中传递一个回调函数作为第二个参数。这个回调函数将在状态更新完成后被调用。\n - 例如：\n ```javascript\n this.setState({ count: this.state.count + 1 }, () => {\n console.log(this.state.count);\n });\n ```\n - 在这个例子中，回调函数将在状态更新完成后被调用，此时可以确保`count`的值已经更新。\n\n在 React 中，调用`setState`方法会触发一系列的操作，包括排队状态更新请求、合并状态、触发重新渲染等。\n",{"_58":285,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/983/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/983/timeline",{"_58":288,"_60":61,"_62":289,"_64":290,"_66":291,"_68":292,"_70":293,"_72":294,"_74":295,"_76":296,"_78":297,"_111":298,"_131":132,"_133":24,"_134":-5,"_135":314,"_137":315,"_159":152,"_153":317,"_155":318,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":319,"_169":320,"_175":321,"_177":322,"_189":324,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/969","https://api.github.com/repos/pro-collection/interview-question/issues/969/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/969/comments","https://api.github.com/repos/pro-collection/interview-question/issues/969/events","https://github.com/pro-collection/interview-question/issues/969",2569718896,"I_kwDOJGDC6c6ZKsxw",969,"http 缓存中 no-cache 与 no-store 的区别是什么【热度: 564】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[299,306,313],{"_70":300,"_72":301,"_58":302,"_117":303,"_119":304,"_121":24,"_122":305},5232529101,"LA_kwDOJGDC6c8AAAABN-IOzQ","https://api.github.com/repos/pro-collection/interview-question/labels/%E7%BD%91%E7%BB%9C","网络","1A8829","web 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当设置了`no-cache`指令时，这并不意味着不使用缓存。相反，它表示在使用缓存之前，必须先与服务器进行验证，以确定缓存的资源是否仍然有效。\n - 这意味着浏览器在使用缓存的资源之前，会向服务器发送一个条件请求（通常是使用`If-Modified-Since`或`If-None-Match`头部），询问服务器该资源是否有更新。如果服务器返回 304 Not Modified 状态码，表示资源没有更新，浏览器可以使用缓存的资源；如果服务器返回新的资源内容，表示资源有更新，浏览器需要使用新的资源。\n\n2. **使用场景**：\n - 适用于需要确保获取到最新资源，但又不想每次都从服务器获取完整资源的情况。例如，对于一些经常更新但更新频率不高的资源，可以使用`no-cache`指令，以便在资源没有更新时可以快速使用缓存，而在资源有更新时可以获取到最新的资源。\n - 对于一些需要根据用户的特定请求参数来生成资源的情况，也可以使用`no-cache`指令，以便在每次请求时都让服务器根据请求参数来确定是否返回缓存的资源还是生成新的资源。\n\n**二、`no-store`**\n\n1. **含义**：\n\n - `no-store`指令表示绝对不允许缓存资源。这意味着浏览器在接收到带有`no-store`指令的响应后，不会将资源存储在任何缓存中，包括浏览器缓存、代理服务器缓存等。每次请求都必须从服务器获取最新的资源。\n\n2. **使用场景**：\n - 适用于对安全性要求非常高的资源，例如包含敏感信息的页面或需要严格保证每次都获取到最新数据的资源。\n - 对于一些动态生成的资源，其内容可能会根据不同的请求而变化，并且不希望这些资源被缓存，可以使用`no-store`指令。例如，一些在线银行页面、交易系统等可能会使用`no-store`指令来确保用户每次看到的都是最新的信息。\n\n总之，`no-cache`表示在使用缓存之前需要与服务器进行验证，而`no-store`表示绝对不允许缓存资源。根据不同的需求，可以选择合适的缓存指令来控制资源的缓存行为。\n",{"_58":323,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/969/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/969/timeline",{"_58":326,"_60":61,"_62":327,"_64":328,"_66":329,"_68":330,"_70":331,"_72":332,"_74":333,"_76":334,"_78":335,"_111":336,"_131":132,"_133":24,"_134":-5,"_135":339,"_137":340,"_159":152,"_153":353,"_155":354,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":355,"_169":356,"_175":357,"_177":358,"_189":360,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/968","https://api.github.com/repos/pro-collection/interview-question/issues/968/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/968/comments","https://api.github.com/repos/pro-collection/interview-question/issues/968/events","https://github.com/pro-collection/interview-question/issues/968",2569699304,"I_kwDOJGDC6c6ZKn_o",968,"如何进行代码质量检测【热度: 497】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[337,338],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":341,"_68":342,"_62":343,"_70":344,"_72":345,"_74":346,"_76":347,"_122":348,"_147":349,"_149":350,"_151":152,"_131":132,"_153":351,"_155":352,"_157":-5,"_158":-5},"https://api.github.com/repos/pro-collection/interview-question/milestones/4","https://github.com/pro-collection/interview-question/milestone/4","https://api.github.com/repos/pro-collection/interview-question/milestones/4/labels",9124550,"MI_kwDOJGDC6c4AizrG",4,"资深","资深级别面试问题",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},50,"2023-03-06T15:00:45Z","2025-07-06T12:02:25Z","2024-10-07T08:15:54Z","2024-10-07T08:15:55Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：代码质量检查\n\n> 作者备注\n>\n> 开发性质的话题，没有统一答复，也没有最好答复，这边给几个思考的方向\n\n进行代码质量检测可以从以下几个方面入手：\n\n**一、静态代码分析**\n\n1. 使用静态代码分析工具\n\n - 例如 SonarQube、Checkstyle、PMD 等。这些工具可以检查代码中的潜在问题，如代码风格不符合规范、未使用的变量、复杂度过高的方法等。\n - SonarQube 可以对多种编程语言进行分析，提供全面的代码质量报告，包括代码重复率、代码复杂度、潜在的漏洞等。\n - Checkstyle 主要用于检查 Java 代码是否符合编码规范，如缩进、命名规范、注释等。\n - PMD 可以检测 Java 代码中的各种问题，如空指针引用、资源未释放等。\n\n2. 遵循编码规范\n - 制定统一的编码规范，包括命名规范、缩进风格、注释规范等。确保团队成员都遵循这些规范，以提高代码的可读性和可维护性。\n - 例如，在 Java 中，变量名通常采用驼峰命名法，方法名采用动词+名词的形式。\n\n**二、单元测试**\n\n1. 编写单元测试用例\n\n - 针对代码中的每个函数、方法或类编写单元测试用例，确保代码的正确性。单元测试应该覆盖各种输入情况，包括正常情况和边界情况。\n - 例如，对于一个加法函数，可以编写测试用例来测试两个正数相加、一个正数和一个负数相加、两个负数相加等情况。\n\n2. 使用测试框架\n - 如 JUnit（Java）、pytest（Python）等。这些测试框架提供了方便的断言方法和测试运行环境，使单元测试的编写和执行更加容易。\n - JUnit 提供了注解和断言方法，方便编写和组织单元测试。可以使用@Test 注解标记测试方法，使用断言方法如 assertEquals、assertTrue 等来验证测试结果。\n\n**三、代码审查**\n\n1. 团队成员之间进行代码审查\n\n - 定期进行代码审查，让其他团队成员对代码进行审查。这可以发现代码中的潜在问题、提高代码质量，并促进团队成员之间的知识共享。\n - 在代码审查中，可以关注代码的可读性、可维护性、性能、安全性等方面。\n\n2. 自动化代码审查工具\n - 如 Gerrit、Phabricator 等。这些工具可以帮助管理代码审查流程，记录审查意见和修改历史，确保代码审查的有效性和可追溯性。\n - Gerrit 可以与版本控制系统集成，提供代码审查、合并请求管理等功能。审查者可以在网页上对代码进行审查，提出意见和建议，开发者可以根据审查意见进行修改。\n\n**四、持续集成和持续部署（CI/CD）**\n\n1. 建立 CI/CD 流程\n\n - 使用工具如 Jenkins、GitLab CI/CD 等建立持续集成和持续部署流程。每次代码提交后，自动触发构建、测试和部署流程，确保代码的质量和稳定性。\n - 在 CI/CD 流程中，可以集成静态代码分析、单元测试、代码审查等环节，及时发现和修复代码中的问题。\n\n2. 监控和反馈\n - 建立监控系统，实时监测应用的性能和可用性。如果出现问题，及时反馈给开发团队，以便进行修复。\n - 可以使用监控工具如 Prometheus、Grafana 等，设置报警规则，当指标超过阈值时及时通知开发团队。\n\n**五、性能测试**\n\n1. 进行性能测试\n\n - 使用性能测试工具如 JMeter、LoadRunner 等对应用进行性能测试。模拟多用户并发访问，测试应用的响应时间、吞吐量、资源利用率等指标。\n - 根据性能测试结果，优化代码的性能，如优化数据库查询、减少网络请求、提高算法效率等。\n\n2. 压力测试\n - 进行压力测试，模拟高负载情况下应用的表现。这可以帮助发现应用在极端情况下的性能问题和潜在的瓶颈。\n - 压力测试可以逐渐增加负载，观察应用的性能变化，直到达到系统的极限。\n",{"_58":359,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/968/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/968/timeline",{"_58":362,"_60":61,"_62":363,"_64":364,"_66":365,"_68":366,"_70":367,"_72":368,"_74":369,"_76":370,"_78":371,"_111":372,"_131":132,"_133":24,"_134":-5,"_135":375,"_137":376,"_159":152,"_153":378,"_155":379,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":380,"_169":381,"_175":382,"_177":383,"_189":385,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/939","https://api.github.com/repos/pro-collection/interview-question/issues/939/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/939/comments","https://api.github.com/repos/pro-collection/interview-question/issues/939/events","https://github.com/pro-collection/interview-question/issues/939",2552998537,"I_kwDOJGDC6c6YK6qJ",939,"手写实现 lodash.flattenDeep 将array递归为一维数组【热度: 345】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[373,374],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":377,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-09-27T13:48:50Z","2024-09-27T13:48:51Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：lodash.flattenDeep 实现\n\n以下是用 JavaScript 手写实现类似于 `lodash.flattenDeep` 的函数来将数组递归展平为一维数组：\n\n```javascript\nfunction flattenDeep(arr) {\n let result = [];\n for (let item of arr) {\n if (Array.isArray(item)) {\n result = result.concat(flattenDeep(item));\n } else {\n result.push(item);\n }\n }\n return result;\n}\n```\n\n你可以使用以下方式测试这个函数：\n\n```javascript\nconst nestedArray = [1, [2, [3, [4]]]];\nconst flattenedArray = flattenDeep(nestedArray);\nconsole.log(flattenedArray); // [1, 2, 3, 4]\n```\n",{"_58":384,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/939/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/939/timeline",{"_58":387,"_60":61,"_62":388,"_64":389,"_66":390,"_68":391,"_70":392,"_72":393,"_74":394,"_76":395,"_78":396,"_111":397,"_131":132,"_133":24,"_134":-5,"_135":400,"_137":401,"_159":152,"_153":403,"_155":404,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":405,"_169":406,"_175":407,"_177":408,"_189":410,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/936","https://api.github.com/repos/pro-collection/interview-question/issues/936/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/936/comments","https://api.github.com/repos/pro-collection/interview-question/issues/936/events","https://github.com/pro-collection/interview-question/issues/936",2540659835,"I_kwDOJGDC6c6Xb2R7",936,"[Vue] 对比一下 vuex 和 Pinia 两个状态库【热度: 300】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[398,399],{"_70":114,"_72":115,"_58":116,"_117":118,"_119":120,"_121":24,"_122":123},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":402,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-09-22T06:11:54Z","2024-09-22T06:11:55Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：vue 状态库对比\n\nVuex 和 Pinia 都是用于 Vue 应用程序的状态管理库，它们有一些相似之处，但也存在一些差异。以下是它们的对比：\n\n**一、相似之处**\n\n1. **集中式状态管理**：\n\n - 两者都提供了一种集中式的方式来管理应用程序的状态。这使得状态可以在不同的组件之间共享，并且可以更容易地跟踪和调试状态的变化。\n - 例如，在一个电商应用中，用户的购物车状态可以存储在状态管理库中，以便在不同的页面和组件中访问和更新。\n\n2. **响应式状态**：\n - Vuex 和 Pinia 都与 Vue 的响应式系统集成，使得状态的变化可以自动触发相关组件的重新渲染。\n - 当购物车中的商品数量发生变化时，相关的组件可以自动更新以反映这个变化。\n\n**二、不同之处**\n\n1. **语法和 API**：\n\n - **Pinia**：\n\n - Pinia 提供了一种更加简洁和直观的 API。它使用类似于 Vue 组件的语法来定义状态和操作，使得代码更加易读和易于维护。\n - 例如，定义一个 store 可以像这样：\n\n ```javascript\n import { defineStore } from \"pinia\";\n\n export const useCartStore = defineStore(\"cart\", {\n state: () => ({\n items: [],\n }),\n actions: {\n addItem(item) {\n this.items.push(item);\n },\n },\n });\n ```\n\n - **Vuex**：\n\n - Vuex 的语法相对较为复杂，需要定义 mutations、actions 和 getters 等不同的概念来管理状态。\n - 例如，定义一个 store 可能如下所示：\n\n ```javascript\n import Vuex from \"vuex\";\n\n const store = new Vuex.Store({\n state: {\n items: [],\n },\n mutations: {\n ADD_ITEM(state, item) {\n state.items.push(item);\n },\n },\n actions: {\n addItem({ commit }, item) {\n commit(\"ADD_ITEM\", item);\n },\n },\n getters: {\n cartItems: (state) => state.items,\n },\n });\n ```\n\n2. **模块系统**：\n\n - **Pinia**：\n\n - Pinia 的模块系统更加灵活和易于使用。可以轻松地将 store 拆分为多个模块，并且可以在不同的模块之间共享状态和操作。\n - 例如，可以创建一个名为`user`的模块和一个名为`cart`的模块，并在它们之间共享一些状态和操作：\n\n ```javascript\n import { defineStore } from \"pinia\";\n\n const useUserStore = defineStore(\"user\", {\n //...\n });\n\n const useCartStore = defineStore(\"cart\", {\n state: () => ({\n //...\n }),\n actions: {\n addItem(item) {\n // 可以访问 userStore 的状态\n if (useUserStore().isLoggedIn) {\n //...\n }\n },\n },\n });\n ```\n\n - **Vuex**：\n - Vuex 的模块系统也很强大，但相对来说更加复杂。需要使用命名空间来区分不同模块的 actions、mutations 和 getters，并且在模块之间共享状态和操作需要一些额外的配置。\n\n3. **类型支持**：\n\n - **Pinia**：\n\n - Pinia 对 TypeScript 的支持非常好，可以轻松地为 store 定义类型，并且在开发过程中可以获得更好的类型提示和错误检查。\n - 例如，可以使用 TypeScript 来定义一个 store 的类型：\n\n ```javascript\n import { defineStore } from 'pinia';\n\n interface CartItem {\n id: number;\n name: string;\n price: number;\n }\n\n export const useCartStore = defineStore('cart', {\n state: () => ({\n items: [] as CartItem[],\n }),\n //...\n });\n ```\n\n - **Vuex**：\n - Vuex 也支持 TypeScript，但相对来说需要一些额外的配置和类型定义文件来获得更好的类型支持。\n\n4. **开发体验**：\n - **Pinia**：\n - Pinia 提供了一些开发工具，如 Pinia Devtools，可以方便地调试和检查 store 的状态和操作。它还与 Vue Devtools 集成，使得在开发过程中可以更好地跟踪状态的变化。\n - Pinia 的 API 更加简洁，使得开发过程更加高效和愉快。\n - **Vuex**：\n - Vuex 也有一些开发工具，如 Vuex Devtools，但相对来说功能可能没有 Pinia Devtools 那么强大。\n - Vuex 的语法相对较为复杂，可能需要一些时间来适应和掌握。\n\n总的来说，Pinia 和 Vuex 都是强大的状态管理库，选择哪一个取决于你的具体需求和个人偏好。如果你喜欢简洁和直观的 API，并且对 TypeScript 有较好的支持需求，那么 Pinia 可能是一个更好的选择。如果你已经熟悉 Vuex 并且对其功能和模块系统有特定的需求，那么 Vuex 也是一个可靠的选择。\n",{"_58":409,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/936/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/936/timeline",{"_58":412,"_60":61,"_62":413,"_64":414,"_66":415,"_68":416,"_70":417,"_72":418,"_74":419,"_76":420,"_78":421,"_111":422,"_131":132,"_133":24,"_134":-5,"_135":425,"_137":426,"_159":152,"_153":428,"_155":429,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":430,"_169":431,"_175":432,"_177":433,"_189":435,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/891","https://api.github.com/repos/pro-collection/interview-question/issues/891/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/891/comments","https://api.github.com/repos/pro-collection/interview-question/issues/891/events","https://github.com/pro-collection/interview-question/issues/891",2529871150,"I_kwDOJGDC6c6WysUu",891,"发送请求的时候， method = OPTIONS 是什么请求【热度: 717】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[423,424],{"_70":300,"_72":301,"_58":302,"_117":303,"_119":304,"_121":24,"_122":305},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":427,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-09-17T02:54:39Z","2024-09-17T02:54:40Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：预检请求\n\n当看到 method 为 `OPTIONS` 的请求时，这是一个 HTTP OPTIONS 请求。OPTIONS 请求是 HTTP/1.1 协议中定义的一种方法，用于获取目的资源（服务器）支持的通信选项。这种请求主要被用于 CORS（Cross-Origin Resource Sharing，跨域资源共享）预检请求，在真正的跨域请求被发送之前执行。\n\n### 作用和目的\n\n- **确定服务器的支持性**：客户端通过发送一个 OPTIONS 请求来确定服务器支持的 HTTP 方法（如 GET、POST、DELETE 等）。\n- **CORS 预检请求**：在发送实际的跨域请求前，浏览器会自动发出一个 OPTIONS 预检请求，询问目标资源的服务器是否允许该跨域请求。这个步骤用来确保安全，避免非法站点调用敏感资源。\n\n### CORS 预检请求内容\n\n在 CORS 上下文中，OPTIONS 请求会包含一些 HTTP 头，指明了实际请求将会使用哪些 HTTP 方法和头部。服务器响应该请求时会指明允许的方法、头部和是否允许带有凭证的请求（如 Cookies）。重要的 HTTP 头包括：\n\n- **`Access-Control-Request-Method`**：在预检请求中，这个头部告诉服务器实际请求将使用的 HTTP 方法是什么。\n\n- **`Access-Control-Request-Headers`**：当实际请求中需要携带额外的头部时，这个字段会列出它们。\n\n- **`Access-Control-Allow-Methods`**：在响应中，这个头部告诉客户端服务器允许的方法。\n\n- **`Access-Control-Allow-Headers`**：在响应中，这个头部告诉客户端服务器允许的头部。\n\n- **`Access-Control-Allow-Origin`**：这个头部指明了哪些源可以访问该资源。如果服务器支持请求的源，则会在响应中包含这个头部。\n\n### 示例\n\n当您的 Web 应用尝试从另一个域名（源）的服务器获取资源时，浏览器会首先发起一个 OPTIONS 请求。例如，如果您的前端应用运行在 `http://example.com` 并尝试通过 AJAX 请求 `http://api.example.com/data`，浏览器会先发送 OPTIONS 请求到 `http://api.example.com/data`。服务器响应该请求后，如果允许此类请求，则浏览器会继续发起实际的 GET/POST/等请求；如果不允许，则停止请求。\n\n总的来说，OPTIONS 请求是 HTTP 规范的一部分，它是 CORS 预检机制中非常重要的一步，用于在实际跨域请求发出之前确定通信的可能性和条件。\n",{"_58":434,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/891/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/891/timeline",{"_58":437,"_60":61,"_62":438,"_64":439,"_66":440,"_68":441,"_70":442,"_72":443,"_74":444,"_76":445,"_78":446,"_111":447,"_131":132,"_133":24,"_134":-5,"_135":456,"_137":457,"_159":152,"_153":459,"_155":459,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":460,"_169":461,"_175":462,"_177":463,"_189":465,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/881","https://api.github.com/repos/pro-collection/interview-question/issues/881/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/881/comments","https://api.github.com/repos/pro-collection/interview-question/issues/881/events","https://github.com/pro-collection/interview-question/issues/881",2526780781,"I_kwDOJGDC6c6Wm51t",881,"flex 布局中子元素不压缩，该如何设置属性【热度: 200】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[448,455],{"_70":449,"_72":450,"_58":451,"_117":452,"_119":453,"_121":24,"_122":454},5232524505,"LA_kwDOJGDC6c8AAAABN-H82Q","https://api.github.com/repos/pro-collection/interview-question/labels/CSS","CSS","A46719","CSS 相关问题",{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":458,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-09-15T07:23:15Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：flex 子元素不压缩\n\n在 Flex 布局中，如果你想要子元素在容器内不被压缩，即保持其原始尺寸或指定尺寸，不受容器大小变化的影响，可以通过设置子元素的`flex-shrink`属性来实现。`flex-shrink`属性决定了当父容器大小小于其所有 flex 项总大小时，各 flex 项的缩小比例。默认值是 1，表示 flex 项会等比例缩小，以适应父容器的大小。\n\n要阻止子元素压缩，你应该将它的`flex-shrink`属性设置为 0。这样，无论容器大小如何变化，子元素都不会缩小。\n\n示例如下：\n\nHTML:\n\n```html\n

不压缩的项目

\n \n

\n```\n\nCSS:\n\n```css\n.flex-container {\n display: flex;\n /* 添加其他需要的flex布局属性 */\n}\n\n.flex-item {\n flex-shrink: 0; /* 这使得该flex项目不会被压缩 */\n /* 设置宽度或其他样式 */\n}\n```\n\n在这个例子中，任何带有`flex-item`类的元素都不会在容器空间不足时被压缩。\n\n此外，`flex`属性是`flex-grow`、`flex-shrink`和`flex-basis`这三个属性的简写。如果你想在保证元素不被压缩的同时，具体控制元素的放大行为或基础大小，也可以直接使用`flex`属性进行设置。例如，如果你还希望元素不放大，并且有一个固定的基础大小，可以这样设置：\n\n```css\n.flex-item {\n flex: 0 0 auto; /* 不放大，不缩小，基础大小为auto */\n}\n```\n\n这种方式提供了更细致的控制，`0 0 auto`分别对应`flex-grow`、`flex-shrink`和`flex-basis`的值。这告诉浏览器该项目即不应放大，也不应缩小，并且以其默认大小作为基础大小。\n",{"_58":464,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/881/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/881/timeline",{"_58":467,"_60":61,"_62":468,"_64":469,"_66":470,"_68":471,"_70":472,"_72":473,"_74":474,"_76":475,"_78":476,"_111":477,"_131":132,"_133":24,"_134":-5,"_135":480,"_137":481,"_159":152,"_153":483,"_155":483,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":484,"_169":485,"_175":486,"_177":487,"_189":489,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/876","https://api.github.com/repos/pro-collection/interview-question/issues/876/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/876/comments","https://api.github.com/repos/pro-collection/interview-question/issues/876/events","https://github.com/pro-collection/interview-question/issues/876",2526772397,"I_kwDOJGDC6c6Wm3yt",876,"eslint 如何设置只校验本次 MR 变更的文件内容【热度: 200】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[478,479],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":482,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-09-15T06:58:14Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：eslint 和 git 结合校验\n\n要让 ESLint 只校验在 Merge Request (MR)、Pull Request (PR)或代码提交中变更的文件，可以采用几种方法。下面是几个可能的方案：\n\n### 1. 命令行 Git 和 ESLint 组合使用\n\n通过组合`git`命令和`eslint`命令来实现。首先，使用`git diff`获取变更的文件列表，然后将这些文件传递给`eslint`进行校验。\n\n```bash\n# 获取master分支与当前分支变更的文件列表，然后对这些文件执行eslint校验\ngit diff --name-only --diff-filter=d master | grep '\\.js$' | xargs eslint\n```\n\n这里的命令解释：\n\n- `git diff --name-only --diff-filter=d master`：获取相对于`master`分支变更的文件列表，`--diff-filter=d`表示排除已删除的文件。\n- `grep '\\.js$'`：过滤出`.js`结尾的文件。\n- `xargs eslint`：将过滤后的文件列表作为参数传递给`eslint`命令。\n\n注意：这个命令以`master`分支作为对比对象，如果你需要对比其他分支，请将`master`替换为相应的分支名。\n\n### 2. 使用 lint-staged 运行 ESLint\n\n[lint-staged](https://github.com/okonet/lint-staged) 是一个在 git 暂存文件上运行 linters 的工具，它非常适合与 pre-commit 钩子结合使用，确保只有符合代码规范的代码才能被提交。\n\n首先，安装`lint-staged`和`husky`（用于管理 git 钩子的工具）：\n\n```bash\nnpm install lint-staged husky --save-dev\n```\n\n然后，你可以在项目的`package.json`文件中配置`lint-staged`：\n\n```json\n{\n \"husky\": {\n \"hooks\": {\n \"pre-commit\": \"lint-staged\"\n }\n },\n \"lint-staged\": {\n \"*.js\": [\"eslint --fix\", \"git add\"]\n }\n}\n```\n\n这样配置后，每次执行`git commit`操作时，`husky`会触发`pre-commit`钩子，运行`lint-staged`，再由`lint-staged`运行 ESLint 检查所有暂存的`.js`文件。通过这种方式，只有变更的并且被 git track 的文件会被 ESLint 校验。\n\n### 3. CI/CD 中集成 ESLint\n\n在持续集成/持续部署 (CI/CD) 流程中，你也可以配置脚本使用类似于第一个方案的命令，只校验在 MR/PR 中变更的文件。具体实现方式会依赖于你使用的 CI/CD 工具（如 GitLab CI、GitHub Actions、Jenkins 等）。\n\n通过在 CI/CD 流程中加入这一步，可以确保只有通过 ESLint 校验的代码变更才能合并到主分支。\n",{"_58":488,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/876/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/876/timeline",{"_58":491,"_60":61,"_62":492,"_64":493,"_66":494,"_68":495,"_70":496,"_72":497,"_74":498,"_76":499,"_78":500,"_111":501,"_131":132,"_133":24,"_134":-5,"_135":510,"_137":511,"_159":194,"_153":513,"_155":514,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":515,"_169":516,"_175":517,"_177":518,"_189":520,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/874","https://api.github.com/repos/pro-collection/interview-question/issues/874/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/874/comments","https://api.github.com/repos/pro-collection/interview-question/issues/874/events","https://github.com/pro-collection/interview-question/issues/874",2498696947,"I_kwDOJGDC6c6U7xbz",874,"如何开启 ts 类型强校验，ts 类型错误 webpack 直接编译失败【热度: 232】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[502,509],{"_70":503,"_72":504,"_58":505,"_117":506,"_119":507,"_121":24,"_122":508},5232527330,"LA_kwDOJGDC6c8AAAABN-IH4g","https://api.github.com/repos/pro-collection/interview-question/labels/TypeScript","TypeScript","258B51","TypeScript 语法部分",{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":512,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-08-31T07:09:46Z","2024-08-31T07:38:22Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：ts 类型强校验\n\n要开启 TypeScript 的类型强校验，并使得 Webpack 在遇到类型错误时编译失败，可以通过以下步骤实现：\n\n### 1. 开启 TS 严格模式\n\n首先，在`tsconfig.json`中启用严格模式。这是通过设置`\"strict\": true`来实现的，这个选项会启用一系列严格的类型检查，帮助你写出更健壮的代码。\n\n```json\n{\n \"compilerOptions\": {\n \"strict\": true,\n ...\n },\n ...\n}\n```\n\n`\"strict\": true`基本等同于下面这些选项全部开启：\n\n- `noImplicitAny`\n- `strictNullChecks`\n- `strictFunctionTypes`\n- `strictBindCallApply`\n- `strictPropertyInitialization`\n- `noImplicitThis`\n- `alwaysStrict`\n\n### 2. 使用`ForkTsCheckerWebpackPlugin`并配置使编译失败\n\n当使用 Webpack 和`ts-loader`时，你可以通过安装并配置`ForkTsCheckerWebpackPlugin`来进行强类型校验。这个插件可以并行运行 TypeScript 类型检查器和 ESLint，并能在检测到错误时使 Webpack 编译失败。\n\n首先，安装`ForkTsCheckerWebpackPlugin`（如果你还没安装）：\n\n```bash\nnpm install --save-dev fork-ts-checker-webpack-plugin\n```\n\n然后，在你的`webpack.config.js`配置文件中，修改`ForkTsCheckerWebpackPlugin`的配置，确保在遇到 TypeScript 类型错误时构建失败：\n\n```javascript\nconst ForkTsCheckerWebpackPlugin = require('fork-ts-checker-webpack-plugin');\n\nmodule.exports = {\n ... // 其他webpack配置\n plugins: [\n new ForkTsCheckerWebpackPlugin({\n async: false, // 关键配置：这将使得webpack等待TypeScript类型检查器和ESLint完成，如果发现任何错误都将导致构建失败\n }),\n ],\n ... // 其他webpack配置\n};\n```\n\n### 注意\n\n- 设置`async: false`，会使得 Webpack 等待类型检查完成，如果有任何错误则构建失败。这对于生产构建很有用，但可能会降低开发环境的迭代速度。\n\n- 由于这个插件是并行在一个单独的进程中运行的，它不会延长 Webpack 的编译时间。然而，如果设置了`async: false`，则 Webpack 会等待该插件的结果，从而影响到构建的总时间。\n",{"_58":519,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/874/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/874/timeline",{"_58":522,"_60":61,"_62":523,"_64":524,"_66":525,"_68":526,"_70":527,"_72":528,"_74":529,"_76":530,"_78":531,"_111":532,"_131":132,"_133":24,"_134":-5,"_135":541,"_137":542,"_159":152,"_153":544,"_155":544,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":545,"_169":546,"_175":547,"_177":548,"_189":550,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/869","https://api.github.com/repos/pro-collection/interview-question/issues/869/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/869/comments","https://api.github.com/repos/pro-collection/interview-question/issues/869/events","https://github.com/pro-collection/interview-question/issues/869",2498581712,"I_kwDOJGDC6c6U7VTQ",869,"实现阿拉伯数字转中文【热度: 673】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[533,534],{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},{"_70":535,"_72":536,"_58":537,"_117":538,"_119":539,"_121":24,"_122":540},5931045040,"LA_kwDOJGDC6c8AAAABYYSQsA","https://api.github.com/repos/pro-collection/interview-question/labels/%E4%BB%A3%E7%A0%81%E5%AE%9E%E7%8E%B0/%E7%AE%97%E6%B3%95","代码实现/算法","1d76db","代码实现或者算法实现",[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":543,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-08-31T03:12:35Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：数字转中文\n\n将阿拉伯数字转换成中文数字，主要考虑到以下几个转换规则：\n\n1. **基本数字**：0-9 对应的汉字数字。\n2. **单位**：十、百、千、万、亿等。\n3. **规则**：数字从右到左，每 4 位一小节，小节内部和小节之间的转换规则。\n\n### 实现思路\n\n1. 将阿拉伯数字分解成单个数字，从右到左进行处理。\n2. 对每 4 位数字进行处理，即一个小节，处理完再根据小节的位置添加对应的单位（万、亿等）。\n3. 处理当前小节内部的数字，并添加十、百、千的单位，注意去除连续的零，并且在必要时加入“零”字。\n4. 将各个小节合并得到最终结果。\n\n下面的 JavaScript 函数实现了阿拉伯数字到中文数字的基本转换：\n\n```js\nconst number2text = (number, type = \"upper\") => {\n // 配置\n const confs = {\n lower: {\n num: [\"零\", \"一\", \"二\", \"三\", \"四\", \"五\", \"六\", \"七\", \"八\", \"九\"],\n unit: [\"\", \"十\", \"百\", \"千\", \"万\"],\n level: [\"\", \"万\", \"亿\"],\n },\n upper: {\n num: [\"零\", \"壹\", \"贰\", \"叁\", \"肆\", \"伍\", \"陆\", \"柒\", \"捌\", \"玖\"],\n unit: [\"\", \"拾\", \"佰\", \"仟\"],\n level: [\"\", \"万\", \"亿\"],\n },\n decimal: {\n unit: [\"分\", \"角\"],\n },\n maxNumber: 999999999999.99,\n };\n\n // 过滤不合法参数\n if (Number(number) > confs.maxNumber) {\n console.error(`The maxNumber is ${confs.maxNumber}. ${number} is bigger than it!`);\n return false;\n }\n\n const conf = confs[type];\n const numbers = String(Number(number).toFixed(2)).split(\".\");\n const integer = numbers[0].split(\"\");\n const decimal = Number(numbers[1]) === 0 ? [] : numbers[1].split(\"\");\n\n // 四位分级\n const levels = integer.reverse().reduce((pre, item, idx) => {\n let level = pre[0] && pre[0].length < 4 ? pre[0] : [];\n let value = item === \"0\" ? conf.num[item] : conf.num[item] + conf.unit[idx % 4];\n level.unshift(value);\n\n if (level.length === 1) {\n pre.unshift(level);\n } else {\n pre[0] = level;\n }\n\n return pre;\n }, []);\n\n // 整数部分\n const _integer = levels.reduce((pre, item, idx) => {\n let _level = conf.level[levels.length - idx - 1];\n let _item = item.join(\"\").replace(/(零)\\1+/g, \"$1\"); // 连续多个零字的部分设置为单个零字\n\n // 如果这一级只有一个零字，则去掉这级\n if (_item === \"零\") {\n _item = \"\";\n _level = \"\";\n\n // 否则如果末尾为零字，则去掉这个零字\n } else if (_item[_item.length - 1] === \"零\") {\n _item = _item.slice(0, _item.length - 1);\n }\n\n return pre + _item + _level;\n }, \"\");\n\n // 小数部分\n let _decimal = decimal\n .map((item, idx) => {\n const unit = confs.decimal.unit;\n const _unit = item !== \"0\" ? unit[unit.length - idx - 1] : \"\";\n\n return `${conf.num[item]}${_unit}`;\n })\n .join(\"\");\n\n // 如果是整数，则补个整字\n return `${_integer}元` + (_decimal || \"整\");\n};\n```\n",{"_58":549,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/869/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/869/timeline",{"_58":552,"_60":61,"_62":553,"_64":554,"_66":555,"_68":556,"_70":557,"_72":558,"_74":559,"_76":560,"_78":561,"_111":562,"_131":132,"_133":24,"_134":-5,"_135":565,"_137":566,"_159":152,"_153":568,"_155":568,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":569,"_169":570,"_175":571,"_177":572,"_189":574,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/857","https://api.github.com/repos/pro-collection/interview-question/issues/857/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/857/comments","https://api.github.com/repos/pro-collection/interview-question/issues/857/events","https://github.com/pro-collection/interview-question/issues/857",2494831272,"I_kwDOJGDC6c6UtBqo",857,"可有办法判断用户的网络条件, 判断网速快慢，网络状态？【热度: 195】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[563,564],{"_70":300,"_72":301,"_58":302,"_117":303,"_119":304,"_121":24,"_122":305},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":567,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-08-29T15:18:24Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：网络状态\n\n确定用户的网络条件，包括网络速度和连接状态，对于提供优质用户体验至关重要。以下是一些方法可以帮助你判断用户的网络条件：\n\n### 1. **Navigator Connection API**\n\n这个 API 提供有关系统的网络连接的信息，如网络的类型和下载速度。这个 API 的支持度不是全局性的，但在许多现代浏览器上可用。使用这个 API，你可以获取到有关用户网络连接的详细信息。\n\n```javascript\nif (\"connection\" in navigator) {\n const connection = navigator.connection || navigator.mozConnection || navigator.webkitConnection;\n\n console.log(`网络类型: ${connection.effectiveType}`);\n console.log(`估计的下行速度: ${connection.downlink}Mbps`);\n console.log(`RTT: ${connection.rtt}ms`);\n\n // 监听网络类型变化\n connection.addEventListener(\"change\", (e) => {\n console.log(`网络类型变化为: ${connection.effectiveType}`);\n });\n}\n```\n\n- `connection.effectiveType` 提供了网络的类型，如 `'4g'`，`'3g'`，代表网络速度。\n- `connection.downlink` 提供了网络的下载速度信息，单位是 Mbps。\n- `connection.rtt` 提供了来回时间信息，单位是毫秒。\n\n### 2. **观测发送请求的速度**\n\n通过发送一个小请求（可能是一个小文件或 API 请求）并测量它完成的时间，可以粗略地估计当前的网络速度。\n\n```javascript\nlet startTime = new Date().getTime(); // 记录开始时间\nfetch(\"your-small-file-or-api-url\").then((response) => {\n let endTime = new Date().getTime(); // 记录结束时间\n let duration = endTime - startTime; // 请求持续时间\n console.log(`请求持续时间: ${duration}ms`);\n // 根据持续时间和文件大小估计网速\n});\n```\n\n### 3. **监听在线和离线事件**\n\nHTML5 引入了在线和离线事件监听，可以用来简单判断用户是否连接到网络。\n\n```javascript\nwindow.addEventListener(\"online\", () => console.log(\"网络已连接\"));\nwindow.addEventListener(\"offline\", () => console.log(\"网络已断开\"));\n```\n\n根据`navigator.onLine`的属性值，你可以检测用户是否在线。\n\n```javascript\nif (navigator.onLine) {\n console.log(\"用户在线\");\n} else {\n console.log(\"用户离线\");\n}\n```\n\n### 结论\n\n虽然无法精确地测量用户的网速，但以上方法提供了一些手段来估计用户的网络状况。这样的信息可以用来动态调整网站或应用的行为，例如，通过降低图像质量、推迟非关键资源的加载或取消某些动画，以改善慢速连接下的用户体验。\n",{"_58":573,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/857/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/857/timeline",{"_58":576,"_60":61,"_62":577,"_64":578,"_66":579,"_68":580,"_70":581,"_72":582,"_74":583,"_76":584,"_78":585,"_111":586,"_131":132,"_133":24,"_134":-5,"_135":589,"_137":590,"_159":152,"_153":592,"_155":593,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":594,"_169":595,"_175":596,"_177":597,"_189":599,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/738","https://api.github.com/repos/pro-collection/interview-question/issues/738/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/738/comments","https://api.github.com/repos/pro-collection/interview-question/issues/738/events","https://github.com/pro-collection/interview-question/issues/738",2279578472,"I_kwDOJGDC6c6H35to",738,"jsBridge 是什么？原理是啥？【热度: 220】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[587,588],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":591,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-05-05T15:12:09Z","2024-05-05T15:12:10Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：jsBridge 原理\n\n`jsBridge`是一种在 Web 开发中常用的技术，通常指的是 JavaScript Bridge 的缩写，它是一种在 Web 视图（如 WebView）和原生应用之间进行通信的机制。jsBridge 使得原生代码（如 Android 的 Java/Kotlin 或 iOS 的 Objective-C/Swift）能够与嵌入到 WebView 中的 JavaScript 代码相互调用和通信。\n\n在具体实现上，jsBridge 的原理可能因平台而异，但大致的原理如下：\n\n1. **从 JavaScript 调用原生代码**：\n\n - **注册原生函数**：首先，原生应用会在 WebView 中注册一些可以供 JavaScript 调用的方法或函数。\n - **调用原生函数**：然后，JavaScript 可以通过特定的接口调用这些注册的原生方法。这通常是通过注入对象（例如，在 Android 中可以使用`addJavascriptInterface`方法）或监听特定的 URL scheme。\n - **消息传递**：当 JavaScript 需要与原生应用通信时，它会发送消息（或调用方法），这个消息包含必要的指令和数据。\n - **原生处理**：原生代码接收到这个消息后，会执行对应的指令，并将结果返回给 JavaScript（如果需要）。\n\n2. **从原生代码调用 JavaScript**：\n - **执行 JavaScript 代码**：原生应用可以执行 WebView 中的 JavaScript 代码。例如，通过 WebView 的`evaluateJavaScript`（iOS）或`loadUrl(\"javascript:...\")`（Android）方法。\n - **回调 JavaScript**：原生应用还可以通过执行回调函数的方式，将数据或结果传递回 JavaScript。\n\njsBridge 在移动应用开发中尤为重要，因为它提供了一种方式来整合 Web 技术和原生应用功能，让开发者能够利用 Web 技术来编写跨平台的应用，同时还能够访问设备的原生功能，如相机、GPS 等。\n\n这种机制特别适合于混合应用的开发，在这些应用中，部分界面和逻辑使用 Web 技术实现，而另一部分则利用原生代码以获取更好的性能和更丰富的设备功能支持。通过 jsBridge，两种不同的代码和技术可以互相协作，提供统一的用户体验。\n",{"_58":598,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/738/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/738/timeline",{"_58":601,"_60":61,"_62":602,"_64":603,"_66":604,"_68":605,"_70":606,"_72":607,"_74":608,"_76":609,"_78":610,"_111":611,"_131":132,"_133":24,"_134":-5,"_135":614,"_137":615,"_159":152,"_153":617,"_155":618,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":619,"_169":620,"_175":621,"_177":622,"_189":624,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/737","https://api.github.com/repos/pro-collection/interview-question/issues/737/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/737/comments","https://api.github.com/repos/pro-collection/interview-question/issues/737/events","https://github.com/pro-collection/interview-question/issues/737",2279572791,"I_kwDOJGDC6c6H34U3",737,"在 JS 中，如何解决递归导致栈溢出问题？【热度: 269】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[612,613],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":616,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-05-05T14:58:37Z","2024-05-05T14:58:38Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：栈溢出问题\n\n在 JavaScript 中，递归如果执行过深，确实有可能导致“栈溢出(stack overflow)”错误，因为每次函数调用都会向调用栈中添加一个新的帧，而每个线程的调用栈都有其最大容量限制。当这个容量被超过时，就会发生栈溢出。为了解决这个问题，你可以使用几种不同的方法：\n\n### 尾调用优化（Tail Call Optimization）\n\n在 ES6 中，引入了尾调用优化。这意味着如果函数的最后一个操作是返回另一个函数的调用（即尾调用），那么这个调用可以在不增加新栈帧的情况下执行。但是，截至我知识更新的时间，大多数 JavaScript 引擎还没有实现这项优化，或者它在默认情况下并未激活。\n\n### 转化为循环\n\n大多数递归函数都可以重写为循环，这样可以避免调用栈问题。这种方法需要手动维护一个栈来存储必要的状态信息，而这个栈通常是存储在堆（heap）中的数组，不受调用栈大小限制。\n\n例如，下面递归计算阶乘的代码：\n\n```javascript\nfunction factorial(n) {\n if (n === 1) return 1;\n return n * factorial(n - 1);\n}\n```\n\n可以重写为循环形式：\n\n```javascript\nfunction factorial(n) {\n let result = 1;\n for (let i = 2; i <= n; i++) {\n result *= i;\n }\n return result;\n}\n```\n\n### 用 Trampoline 函数\n\nTrampoline 是一个高阶函数，使您可以在递归调用的情况下避免栈溢出。它通过在每个递归步骤返回一个函数而不是值，然后持续调用这些函数，直到获得最终结果为止。\n\n```javascript\nfunction trampoline(fn) {\n return function (...args) {\n let result = fn.apply(this, args);\n\n while (typeof result === \"function\") {\n result = result();\n }\n\n return result;\n };\n}\n```\n\n然后，将原始递归函数改写为每次递归调用返回一个函数：\n\n```javascript\nfunction recursiveFunction(args) {\n if (baseCase) {\n return finalValue;\n } else {\n return function () {\n return recursiveFunction(newArgs);\n };\n }\n}\n\nconst trampolinedFunction = trampoline(recursiveFunction);\n```\n\n调用 `trampolinedFunction` 会避免栈溢出，因为它不是真正的递归调用，只是同步循环调用那些返回的函数。\n\n### 生成器和 Promises\n\n使用 ES6 的生成器(generator)和/或 Promises 也可以用来避免递归调用过深。这些特性可以帮助您生成异步递归调用，其允许事件循环（event loop）介入，避免单次执行过多递归调用造成的栈溢出。\n\n### 使用异步递归\n\n将递归函数改造成异步函数（async function），并确保每一次递归调用都有机会返回控制权给 JavaScript 事件循环，这可以通过`setTimeout`、`setImmediate`或者`process.nextTick`（在 Node.js 环境下）实现。\n\n例如，可以将一个同步递归函数改写为：\n\n```javascript\nfunction recursiveAsyncFunction(i) {\n if (i < 0) return Promise.resolve();\n console.log(\"Recursion \", i);\n return new Promise((resolve) => {\n setImmediate(() => {\n resolve(recursiveAsyncFunction(i - 1));\n });\n });\n}\n```\n\n记得确保递归终止条件是正确的，否则即便以上方法也可能导致无限循环或者内存泄漏。每一种方法都有其适用场景，具体使用哪一种方法取决于问题的具体需求。\n",{"_58":623,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/737/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/737/timeline",{"_58":626,"_60":61,"_62":627,"_64":628,"_66":629,"_68":630,"_70":631,"_72":632,"_74":633,"_76":634,"_78":635,"_111":636,"_131":132,"_133":24,"_134":-5,"_135":639,"_137":640,"_159":152,"_153":642,"_155":643,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":644,"_169":645,"_175":646,"_177":647,"_189":649,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/666","https://api.github.com/repos/pro-collection/interview-question/issues/666/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/666/comments","https://api.github.com/repos/pro-collection/interview-question/issues/666/events","https://github.com/pro-collection/interview-question/issues/666",2079163200,"I_kwDOJGDC6c577YNA",666,"git 仓库迁移应该怎么操作【热度: 160】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[637,638],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":641,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2024-01-12T15:55:20Z","2024-01-12T15:55:21Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：git 仓库迁移\n\n如果你想迁移仓库并保留原始仓库的所有提交历史、分支和标签，你可以使用以下步骤：\n\n### 方法一：使用 `git clone` 和 `git push`\n\n1. **在仓库 B 中创建新的仓库。**\n\n2. **在本地克隆仓库 A：**\n```bash\ngit clone --mirror <仓库 A URL>\ncd <仓库 A 目录>\n```\n\n使用 `--mirror` 选项克隆仓库会保留所有分支、标签和提交历史。\n\n3. **修改远程仓库地址为仓库 B：**\n```bash\ngit remote set-url --push origin <仓库 B URL>\n```\n\n4. **推送到仓库 B：**\n```bash\ngit push --mirror\n```\n\n### 方法二：使用 `git bundle`\n\n1. **在仓库 A 中创建 bundle 文件：**\n```bash\ngit bundle create repoA.bundle --all\n```\n\n2. **将 `repoA.bundle` 文件传输到仓库 B 所在位置。**\n\n3. **在仓库 B 中克隆：**\n```bash\ngit clone repoA.bundle <仓库 B 目录>\n```\n\n这两种方法都会保留所有分支、标签和提交历史。选择哪种方法取决于你的具体需求和迁移环境。\n\n**注意：**\n- 使用 `--mirror` 或 `--all` 选项在 `git clone` 或 `git bundle` 中时，会将所有的分支和标签复制到目标仓库。\n- 在执行之前，请确保仓库 B 是空的或者是一个你可以覆盖的目标仓库，因为这些操作会覆盖目标仓库的内容。\n- 如果仓库 A 中包含子模块，你可能需要额外处理子模块的迁移。\n",{"_58":648,"_180":194,"_181":194,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/666/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/666/timeline",{"_58":651,"_60":61,"_62":652,"_64":653,"_66":654,"_68":655,"_70":656,"_72":657,"_74":658,"_76":659,"_78":660,"_111":661,"_131":132,"_133":24,"_134":-5,"_135":664,"_137":665,"_159":152,"_153":667,"_155":667,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":668,"_169":669,"_175":670,"_177":671,"_189":673,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/640","https://api.github.com/repos/pro-collection/interview-question/issues/640/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/640/comments","https://api.github.com/repos/pro-collection/interview-question/issues/640/events","https://github.com/pro-collection/interview-question/issues/640",1997052702,"I_kwDOJGDC6c53CJse",640,"后端一次性返回树形结构数据，数据量非常大, 前端该如何处理？【热度: 171】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[662,663],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":666,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2023-11-16T14:55:16Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：大数据处理\n\n当后端一次性返回的树形结构数据量非常大，导致前端一次性计算和渲染会栈溢出的情况时，可以考虑以下几种处理方式：\n\n1. 分批处理：将大量的树形数据分为多个批次进行处理和渲染。前端可以通过递归或循环的方式，每次处理一部分数据，并在渲染完成后再处理下一部分数据。这样可以避免一次性处理大量数据造成栈溢出的问题。\n\n2. 异步处理：使用异步处理的方式进行数据的计算和渲染。前端可以利用JavaScript的异步特性，将数据处理和渲染任务分为多个异步任务，并通过事件循环机制依次执行这些任务。这样可以避免一次性计算和渲染大量数据导致栈溢出的问题。\n\n3. 虚拟化渲染：使用虚拟化渲染技术，只渲染当前可见区域的树节点，而不是全部节点。可以根据页面的滚动位置和用户操作，只渲染当前需要展示的节点，而对于不可见的节点只保留其占位符。这样可以减少实际渲染的节点数量，降低内存占用和渲染时间。\n\n4. 数据分级处理：对于树形结构数据，可以考虑对数据进行分级处理。将数据根据节点的层级关系进行分组，每次只处理和渲染当前层级的节点数据。这样可以减少每次处理的数据量，降低栈溢出的风险。\n\n根据具体的业务需求和技术实现情况，可以选择适合的处理方式来解决栈溢出问题。同时，也可以结合多种处理方式来提高页面性能和用户体验。\n",{"_58":672,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/640/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/640/timeline",{"_58":675,"_60":61,"_62":676,"_64":677,"_66":678,"_68":679,"_70":680,"_72":681,"_74":682,"_76":683,"_78":684,"_111":685,"_131":132,"_133":24,"_134":-5,"_135":688,"_137":689,"_159":194,"_153":691,"_155":692,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":693,"_169":694,"_175":695,"_177":696,"_189":698,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/615","https://api.github.com/repos/pro-collection/interview-question/issues/615/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/615/comments","https://api.github.com/repos/pro-collection/interview-question/issues/615/events","https://github.com/pro-collection/interview-question/issues/615",1983708784,"I_kwDOJGDC6c52PP5w",615,"介绍一下迭代器 Iterator, 以及有哪些用法【热度: 645】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[686,687],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":690,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2023-11-08T14:13:30Z","2025-03-06T09:50:17Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：迭代器 Iterator\n\n### 1、Iterator 的概念\n\nJavaScript 原有的表示 “ 集合 ” 的数据结构，主要是数组（ Array ）和对象（ Object ）， ES6 又添加了 Map 和 Set 。\n这样就有了四种数据集合，用户还可以组合使用它们，定义自己的数据结构，比如数组的成员是 Map ， Map 的成员是对象。\n这样就需要一种统一的接口机制，来处理所有不同的数据结构。 \n遍历器（ Iterator ）就是这样一种机制。它是一种接口，为各种不同的数据结构提供统一的访问机制。\n任何数据结构只要部署 Iterator 接口，就可以完成遍历操作（即依次处理该数据结构的所有成员）。 \nIterator 的作用有三个：一是为各种数据结构，提供一个统一的、简便的访问接口；二是使得数据结构的成员能够按某种次序排列；三是 ES6 创造了一种新的遍历命令for...of循环， Iterator 接口主要供for...of消费。\n\nIterator 的遍历过程是这样的。\n- （ 1 ）创建一个指针对象，指向当前数据结构的起始位置。也就是说，遍历器对象本质上，就是一个指针对象。\n- （ 2 ）第一次调用指针对象的next方法，可以将指针指向数据结构的第一个成员。\n- （ 3 ）第二次调用指针对象的next方法，指针就指向数据结构的第二个成员。\n- （ 4 ）不断调用指针对象的next方法，直到它指向数据结构的结束位置。\n\n每一次调用next方法，都会返回数据结构的当前成员的信息。\n具体来说，就是返回一个包含value和done两个属性的对象。其中，value属性是当前成员的值，done属性是一个布尔值，表示遍历是否结束。\n\n\n### 2、数据结构的默认 Iterator 接口\n\nIterator 接口的目的，就是为所有数据结构，提供了一种统一的访问机制，即for...of循环（详见下文）。当使用for...of循环遍历某种数据结构时，该循环会自动去寻找 Iterator 接口。 \n在 ES6 中，有三类数据结构原生具备 Iterator 接口：数组、某些类似数组的对象、 Set 和 Map 结构。\n\n实例：\n```javascript\n let arr = ['a', 'b', 'c'];\n let iter = arr[Symbol.iterator]();\n iter.next() // { value: 'a', done: false }\n iter.next() // { value: 'b', done: false }\n iter.next() // { value: 'c', done: false }\n iter.next() // { value: undefined, done: true }\n```\n\n上面提到，原生就部署 Iterator 接口的数据结构有三类，对于这三类数据结构，不用自己写遍历器生成函数，for...of循环会自动遍历它们。除此之外，其他数据结构（主要是对象）的 Iterator 接口，都需要自己在Symbol.iterator属性上面部署，这样才会被for...of循环遍历。\n\n\n### 3、调用 Iterator 接口的场合\n有一些场合会默认调用 Iterator 接口（即Symbol.iterator方法），除了下文会介绍的for...of循环，还有几个别的场合。\n\n#### 3.1、解构赋值\n对数组和 Set 结构进行解构赋值时，会默认调用Symbol.iterator方法。 \n实例1：\n```javascript\n let set = new Set().add('a').add('b').add('c');\n let [x,y] = set;\n // x='a'; y='b'\n let [first, ...rest] = set;\n // first='a'; rest=['b','c'];\n```\n\n#### 3.2、扩展运算符\n扩展运算符（ ... ）也会调用默认的 iterator 接口。 \n实例2：\n```javascript\n // 例一\n var str = 'hello';\n [...str] // ['h','e','l','l','o']\n // 例二\n let arr = ['b', 'c'];\n ['a', ...arr, 'd']\n // ['a', 'b', 'c', 'd']\n```\n\n#### 3.3、yield*\nyield* 后面跟的是一个可遍历的结构，它会调用该结构的遍历器接口。 \n实例3：\n```javascript\n let generator = function* () {\n yield 1;\n yield* [2,3,4];\n yield 5;\n };\n var iterator = generator();\n iterator.next() // { value: 1, done: false }\n iterator.next() // { value: 2, done: false }\n iterator.next() // { value: 3, done: false }\n iterator.next() // { value: 4, done: false }\n iterator.next() // { value: 5, done: false }\n iterator.next() // { value: undefined, done: true }\n```\n\n#### 3.4、其他场合\n由于数组的遍历会调用遍历器接口，所以任何接受数组作为参数的场合，其实都调用了遍历器接口。下面是一些例子。\n- for...of\n- Array.from()\n- Map(), Set(), WeakMap(), WeakSet() （比如new Map([['a',1],['b',2]])）\n- Promise.all()\n- Promise.race()\n\n\n### 4、Iterator 接口与 Generator 函数\nSymbol.iterator方法的最简单实现，还是使用下一章要介绍的 Generator 函数。 \n实例：\n```javascript\n var myIterable = {};\n myIterable[Symbol.iterator] = function* () {\n yield 1;\n yield 2;\n yield 3;\n };\n [...myIterable] // [1, 2, 3]\n \n // 或者采用下面的简洁写法\n let obj = {\n * [Symbol.iterator]() {\n yield 'hello';\n yield 'world';\n }\n };\n for (let x of obj) {\n console.log(x);\n }\n // hello\n // world\n```\n",{"_58":697,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/615/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/615/timeline",{"_58":700,"_60":61,"_62":701,"_64":702,"_66":703,"_68":704,"_70":705,"_72":706,"_74":707,"_76":708,"_78":709,"_111":710,"_131":132,"_133":24,"_134":-5,"_135":713,"_137":714,"_159":152,"_153":716,"_155":716,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":717,"_169":718,"_175":719,"_177":720,"_189":722,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/613","https://api.github.com/repos/pro-collection/interview-question/issues/613/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/613/comments","https://api.github.com/repos/pro-collection/interview-question/issues/613/events","https://github.com/pro-collection/interview-question/issues/613",1977199006,"I_kwDOJGDC6c512ame",613,"箭头函数的作用以及使用场景【热度: 760】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[711,712],{"_70":208,"_72":209,"_58":210,"_117":211,"_119":212,"_121":24,"_122":213},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":139,"_68":140,"_62":141,"_70":142,"_72":143,"_74":144,"_76":145,"_122":146,"_147":715,"_149":150,"_151":152,"_131":132,"_153":154,"_155":156,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2023-11-04T06:35:45Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**特点**\n\n1. **简洁的语法形式**：箭头函数使用了更简洁的语法形式，省略了传统函数声明中的`function`关键字和大括号。它通常可以在更少的代码行数中表达相同的逻辑。\n2. **没有自己的this**：箭头函数没有自己的`this`绑定，它会捕获所在上下文的`this`值。这意味着箭头函数中的`this`与其定义时所在的上下文中的`this`保持一致，而不是在函数被调用时动态绑定。这可以避免传统函数中常见的`this`指向问题，简化了对`this`的使用和理解。\n3. **没有`arguments`对象**：箭头函数也没有自己的`arguments`对象。如果需要访问函数的参数，可以使用剩余参数（Rest Parameters）或使用展开运算符（Spread Operator）将参数传递给其他函数。\n4. **无法作为构造函数**：箭头函数不能用作构造函数，不能使用`new`关键字调用。它们没有`prototype`属性，因此无法使用`new`关键字创建实例。\n5. **隐式的返回值**：如果箭头函数的函数体只有一条表达式，并且不需要额外的处理逻辑，那么可以省略大括号并且该表达式将隐式作为返回值返回。\n6. **不能绑定自己的this、super、new.target**：由于箭头函数没有自己的`this`绑定，也无法使用`super`关键字引用父类的方法，也无法使用`new.target`获取构造函数的引用。\n\n**作用**\n\n1. **简化普通函数**：箭头函数提供了更简洁的语法形式，可以在需要定义函数的地方使用更短的代码来表达同样的逻辑。这可以提高代码的可读性和维护性。\n2. **保留上下文**：箭头函数没有自己的`this`绑定，它会捕获所在上下文的`this`值。这意味着在箭头函数中，`this`的值是在函数定义时确定的，而不是在函数被调用时动态绑定。这种特性可以避免传统函数中的`this`绑定问题，并使代码更易于理解和维护。\n\n**使用场景**\n\n1. 简化函数表达式：当需要定义一个简单的函数表达式时，可以使用箭头函数代替传统的函数表达式，减少代码量。\n\n ```js\n // 传统函数表达式\n const sum = function(a, b) {\n return a + b;\n };\n\n // 箭头函数\n const sum = (a, b) => a + b;\n ```\n\n2. 箭头函数作为回调函数：当需要传递回调函数时，箭头函数可以提供更简洁的语法形式，同时保留外层上下文中的`this`。\n\n ```js\n // 传统回调函数\n someFunction(function() {\n console.log(this); // 外层上下文的this\n });\n\n // 箭头函数作为回调函数\n someFunction(() => {\n console.log(this); // 外层上下文的this\n });\n ```\n\n3. 简化函数中的`this`绑定问题：由于箭头函数没有自己的`this`绑定，可以避免使用传统函数中常见的`bind`、`call`或`apply`等方法来绑定`this`。\n\n ```js\n // 传统函数中的this绑定\n const obj = {\n value: 42,\n getValue: function() {\n setTimeout(function() {\n console.log(this.value); // undefined，因为此时this指向全局对象\n }, 1000);\n }\n };\n\n // 使用箭头函数避免this绑定问题\n const obj = {\n value: 42,\n getValue: function() {\n setTimeout(() => {\n console.log(this.value); // 42，箭头函数捕获了外层上下文的this\n }, 1000);\n }\n };\n\n // ```\n ```\n",{"_58":721,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/613/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/613/timeline",{"_58":724,"_60":61,"_62":725,"_64":726,"_66":727,"_68":728,"_70":729,"_72":730,"_74":731,"_76":732,"_78":733,"_111":734,"_131":132,"_133":24,"_134":-5,"_135":737,"_137":738,"_159":152,"_153":740,"_155":741,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":742,"_169":743,"_175":744,"_177":745,"_189":747,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/544","https://api.github.com/repos/pro-collection/interview-question/issues/544/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/544/comments","https://api.github.com/repos/pro-collection/interview-question/issues/544/events","https://github.com/pro-collection/interview-question/issues/544",1878538861,"I_kwDOJGDC6c5v-Dpt",544,"web 网页如何禁止别人移除水印【热度: 540】",{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},[735,736],{"_70":307,"_72":308,"_58":309,"_117":310,"_119":311,"_121":24,"_122":312},{"_70":125,"_72":126,"_58":127,"_117":128,"_119":129,"_121":24,"_122":130},[],{"_58":217,"_68":218,"_62":219,"_70":220,"_72":221,"_74":222,"_76":223,"_122":224,"_147":739,"_149":226,"_151":152,"_131":132,"_153":227,"_155":228,"_157":-5,"_158":-5},{"_80":81,"_70":82,"_72":83,"_84":85,"_86":28,"_58":87,"_68":88,"_89":90,"_91":92,"_93":94,"_95":96,"_97":98,"_99":100,"_101":102,"_66":103,"_104":105,"_106":107,"_108":109,"_110":24},"2023-09-02T09:42:16Z","2023-09-02T09:42:17Z",{"_166":152,"_167":152,"_168":152},{"_171":152,"_172":152,"_173":152,"_174":152},"**关键词**：前端防止移除水印\n\n关于加水印的问题，可以看这篇文档： https://github.com/pro-collection/interview-question/issues/351\n\n关于如何防止移除水印：\n\n可以通过监听 DOM 的变化来检测是否有人删除水印，可以使用 `MutationObserver API`。\n`MutationObserver` 可以观察 DOM 树的变化，并在变化发生时触发回调函数。你可以在回调函数中检查是否有水印被删除，然后采取相应的措施。\n\n以下是一个简单的示例代码，演示了如何使用 MutationObserver 监听 DOM 变化：\n\n```javascript\n// 目标节点\nconst targetNode = document.body;\n\n// 创建 MutationObserver 实例\nconst observer = new MutationObserver((mutationsList) => {\n for (let mutation of mutationsList) {\n // 检查是否有子节点被删除\n if (mutation.removedNodes.length > 0) {\n // 在此处判断是否有水印被删除\n // 如果水印被删除，则重新插入水印的 DOM 元素到目标节点\n // 例如： targetNode.appendChild(watermarkElement);\n }\n }\n});\n\n// 配置 MutationObserver\nconst config = { childList: true, subtree: true };\n\n// 开始观察目标节点\nobserver.observe(targetNode, config);\n```\n\n在上述代码中，我们创建了一个 MutationObserver 实例，并通过 `observe` 方法将其绑定到目标节点上。在回调函数中，我们使用 `mutation.removedNodes` 来检查是否有子节点被删除，如果发现水印被删除，则可以采取相应的措施来重新插入水印的 DOM 元素。\n\n需要注意的是，MutationObserver API 是现代浏览器提供的功能，在老旧的浏览器中可能不支持。因此，在实际使用时，你需要对浏览器的兼容性进行测试和处理。\n\n另外，如果水印被删除后立即加回去，你可以在检测到水印被删除时，立即执行插入水印的代码，以确保水印能够迅速地重新出现在页面上。\n",{"_58":746,"_180":152,"_181":152,"_182":152,"_183":152,"_184":152,"_185":152,"_186":152,"_187":152,"_188":152},"https://api.github.com/repos/pro-collection/interview-question/issues/544/reactions","https://api.github.com/repos/pro-collection/interview-question/issues/544/timeline",{"_58":749,"_60":61,"_62":750,"_64":751,"_66":752,"_68":753,"_70":754,"_72":755,"_74":756,"_76":757,"_78":758,"_111":759,"_131":132,"_133":24,"_134":-5,"_135":762,"_137":763,"_159":152,"_153":765,"_155":766,"_158":-5,"_161":162,"_106":-5,"_163":-5,"_164":767,"_169":768,"_175":769,"_177":770,"_189":772,"_191":-5,"_192":-5,"_193":194},"https://api.github.com/repos/pro-collection/interview-question/issues/533","https://api.github.com/repos/pro-collection/interview-question/issues/533/labels{/name}","https://api.github.com/repos/pro-collection/interview-question/issues/533/comments","https://api.github.com/repos/pro-collection/interview-question/issues/533/events","https://github.com/pro-collection/interview-question/issues/533",1867203688,"I_kwDOJGDC6c5vS0Ro",533,"单点登录是什么，具体流程是什么【热度: 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