2026前端面试题（六）

防抖const debounce (fn,delay300) { let timer null return function(...args){ clearTimeout(timer) timer setTimeout(()fn.apply(this.args),delay) } }节流const throttle (fn,delay300){ let lock false return function(...args){ if(!lock){ lock true setTimeout((arg){ fn.apply(this.args) lock false },delay) } } }深拷贝const deepClone (obj,map new Weepmap()) { if(obj null || type obj ! object) return obj if(map.has(obj)) return map.get(obj) const target Array.isArray(obj) ? [] : {} map.set(obj,target) Reflect.ownKeys(obj).forEach(key { target[key] deepClone(obj[key],map) }) return target }手写Promise 简易版class MyPromise{ constructor(executor) { this.state pending this.val null this.onFulfiled [] this.onRejected [] const resolve v { if(this.state ! pending) return this.state fulfiled this.val v this.onFulfiled.forEach(fn fn(v)) } const reject e { if(this.state ! pending) return this.state rejected this.val e this.onRejected.forEach(fn fn(e)) } try { executor(resolve, reject)} catch(err) {reject(err)} } then(suc, err) { suc suc || (v v) err err || (e { throw e }) return new MyPromise((res, rej) { const cb fn v setTimeout(() { try { const r fn(v); res(r) } catch (e) { rej(e) } }) if (this.state fulfilled) cb(suc)(this.val) else if (this.state rejected) cb(err)(this.val) else { this.onFulfilled.push(cb(suc)) this.onRejected.push(cb(err)) } }) } }手写bind/call/bind# call Function.prototype.myCall function(ctx, ...args) { ctx ctx || window ctx.fn this const res ctx.fn(...args) delete ctx.fn return res } # apply Function.propotype.myApply function(ctx, args []) { ctx ctx || window ctx.fn this const res ctx.fn(...args) delete ctx.fn return res } # bind(返回新函数) Function prototype.myBind function(ctx, ...args1) { const fn this return function(...args2) { return fn.myCall(ctx, ...args1, ...args2) } }数组去重、flat扁平化# 数组去重new Set function unique(arr){ return [...new Set(arr)] } # flat 扁平化无限层级 function flat(arr){ return arr.reduce((pre,cur) pre.concat(Array.isArray(cur) ? flat(cur) :cur),[]) }new实现const myNew (fn, ...args) { const obj object.create(Fn.prototype) const res Fn.apply(obj, args) return typeof res object res ! null ? res : obj }instanceOfconst myInstanceof (left, right) { let proto Object.getPrototypeOf(left) while(proto) { if(proto right.prototype) return true proto Object.getPrototypeOf(proto) } return false }发布订阅模式class EventBus{ constructor() { this.events {} } on(type, fn){ if(! this.events[type].push(fn)) } emit(type, ...args) { this.events[type]?.forEach(fn fn(...srgs))) } off(type, fn) { if(!this.events[type]) return this.events[type] this.events[type].filter(item item ! fn) } }简易Ajaxfunction ajax({ url, method GET, data }) { return new Promise((res, rej) { const xhr new XMLHttpRequest() let params if (data) params new URLSearchParams(data).toString() let reqUrl url if (method.toUpperCase() GET params) reqUrl ? params xhr.open(method, reqUrl) if (method.toUpperCase() ! GET) { xhr.setRequestHeader(Content-Type, application/x-www-form-urlencoded) } xhr.onload () xhr.status 200 xhr.status 300 ? res(xhr.response) : rej(xhr.statusText) xhr.onerror () rej(请求失败) xhr.send(method.toUpperCase() GET ? null : params) }) }