Javascript常见面试手写题

// 1. 防抖
export function debounce(fn, delay, options) {let timer = null;let shouldInvoke = options.immediately // 是否立即执行return function(...args) {if (shouldInvoke) {fn.call(this, ...args)shouldInvoke = false}if (timer) {clearTimeout(timer)}timer = setTimeout(() => {fn.call(this, ...args)shouldInvoke = options.immediately}, delay)}
}

// 节流函数
export function throttle(fn, delay) {let timer = nullreturn function (...args) {if (!timer) {fn.call(this, ...args)timer = setTimeout(() => {timer = null}, delay)} }
}

export function uniqueArr(arr) {return [...new Set(arr)];
}export function uniqueArr2(arr) {return arr.filter((value, index) => arr.indexOf(value) === index);
}

// 根据指定深度递归地将所有子数组元素拼接到新的数组中
// n默认1
export function flat(arr, n) {return arr.flat(n)
}// 全部扁平化
export function flat2(arr) {while(arr.some(item => Array.isArray(item))) {arr = [].concat(...arr);}return arr;
}// 递归法
export function flat3(arr, deep) {if (deep === 0) {return arr}let ret = []for (let i = 0 ; i < arr.length ; i ++){if (Array.isArray(arr[i])) {ret.push(...flat3(arr[i], deep - 1))} else {ret.push(arr[i])}}return ret
}

export function deepClone(obj) {if (obj === null || typeof obj!== 'object') {return obj;}if (Array.isArray(obj)) {return obj.map(item => deepClone(item));}const clonedObj = {};for (const key in obj) {if (obj.hasOwnProperty(key)) {clonedObj[key] = deepClone(obj[key]);}}return clonedObj;
}

export class EventEmitter {constructor() {this.events = {};}on(eventName, callback) {if (!this.events[eventName]) {this.events[eventName] = [];}this.events[eventName].push(callback);return this;}emit(eventName,...args) {if (this.events[eventName]) {this.events[eventName].forEach(callback => callback(...args));}return this;}off(eventName, callback) {if (this.events[eventName]) {this.events[eventName] = this.events[eventName].filter(cb => cb!== callback);}return this;}
}// const emitter = new EventEmitter();// const callback1 = (data) => {
//   console.log('Callback 1:', data);
// };// const callback2 = (data) => {
//   console.log('Callback 2:', data);
// };// emitter.on('event1', callback1);
// emitter.on('event1', callback2);// emitter.emit('event1', 'Hello from event emitter!');// emitter.off('event1', callback1);// emitter.emit('event1', 'Another emit after removing callback1.');

export function curry(func) {return function curried(...args) {if (args.length >= func.length) {return func.apply(this, args);} else {return function (...nextArgs) {return curried.apply(this, [...args,...nextArgs]);};}};
}

/*** 从右向左执行* https://juejin.cn/post/6844903910834962446*/
export function compose(...fns) {if(fns.length === 0) {return val => val}return function(val) {fns.reverse().forEach(fn => {val = fn(val)})return val}
}

/*** 指定函数调用次数*/
export function before (fn, times) {return (...args) => {if (times === 0) returnfn(...args)if (times > 0) {times-- }}
}

export function partial(fn, ...arg) {return (...args) => {return fn(...arg, ...args)}
}

// get
export function ajaxGet(url, callback) {const xhr = new XMLHttpRequest();xhr.open('GET', url, true);xhr.onreadystatechange = function () {if (xhr.readyState === 4 && xhr.status === 200) {callback(xhr.responseText);}};xhr.send();
}// post
export function ajaxPost(url, data, callback) {const xhr = new XMLHttpRequest();xhr.open('POST', url, true);xhr.setRequestHeader('Content-Type', 'application/json');xhr.onreadystatechange = function () {if (xhr.readyState === 4) {if (xhr.status === 200 || xhr.status === 201) {callback(xhr.responseText);} else {console.error('Error in POST request:', xhr.statusText);}}};xhr.send(JSON.stringify(data));
}

export function call(context, ...args) {if (context === null || context === undefined) {context = typeof window !== 'undefined' ? window : global} else {context = Object(context) // 原始值会被包装 如果是非原始值会直接返回}context.fn = this;let ret = context.fn(...args)delete context.fnreturn ret
}

export function bind(context, ...args) {if (typeof this !== "function") {throw new TypeError("Error");}let self = thislet fBound = function (...args2) {return self.call(this instanceof self ? this : context, ...args, ...args2)}fBound.prototype = Object.create(self.prototype)return fBound
}

export function apply (context, argsArray) {if (context === null || context === undefined) {context = typeof window !== 'undefined' ? window : global}context.fn = thislet ret = context.fn(...Array.from(argsArray))delete context.fnreturn ret
}

export function _new(constructor, ...args) {  // let obj = {}                            // 1. 创建一个空对象({})// obj.__proto__ = constructor.prototype          // 2. 链接该对象到另外一个对象let obj = Object.create(constructor.prototype)    // 替代1 2const ret = constructor.call(obj, ...args) // 3. 将创建的空对象作为this的上下文return typeof ret === 'object' ? ret : obj // 4. 如果该函数没有返回对象，则返回this
}

export function _instanceof(V, F) {if (Object.prototype.toString.call(V) !== '[object Object]') {return false}let O = F.prototypeif (Object.prototype.toString.call(O) !== '[object Object]') {return false}while(true) {V = Object.getPrototypeOf(V)if (V === null) return falseif (V === O) return true}
}

export function jsonp(url) {return new Promise((resolve, reject) => {// 创建一个唯一的回调函数名const uniqueCallbackName = `jsonp_callback_${Date.now()}_${Math.random().toString(36).substring(2)}`;// 创建一个 script 标签const script = document.createElement('script');script.src = `${url}?callback=${uniqueCallbackName}`;// 定义全局回调函数window[uniqueCallbackName] = function(data) {resolve(data);// 清除全局回调函数和 script 标签delete window[uniqueCallbackName];document.body.removeChild(script);};// 处理错误情况script.onerror = function() {reject(new Error('JSONP request failed'));delete window[uniqueCallbackName];document.body.removeChild(script);};// 将 script 标签添加到文档中document.body.appendChild(script);});
}