Maison > Article > interface Web > Fonctions d'écriture manuscrites courantes de JavaScript
Recommandations d'apprentissage associées : javascript
function debounce(func, ms = 500) { let timer; return function (...args) { if (timer) { clearTimeout(timer); } timer = setTimeout(() => { func.apply(this, args); }, ms); }; }复制代码
function throttle(func, ms) { let canRun = true; return function (...args) { if (!canRun) return; canRun = false; setTimeout(() => { func.apply(this, args); canRun = true; }, ms); }; }复制代码
function myNew(Func) { const instance = {}; if (Func.prototype) { Object.setPrototypeOf(instance, Func.prototype); } const res = Func.apply(instance, [].slice.call(arguments, 1)); if (typeof res === "function" || (typeof res === "object" && res !== null)) { return res; } return instance; }复制代码
Function.prototype.myBind = function (context = globalThis) { const fn = this; const args = Array.from(arguments).slice(1); const newFunc = function () { if (this instanceof newFunc) { // 通过 new 调用,绑定 this 为实例对象 fn.apply(this, args); } else { // 通过普通函数形式调用,绑定 context fn.apply(context, args); } }; // 支持 new 调用方式 newFunc.prototype = fn.prototype; return newFunc; };复制代码
Function.prototype.myCall = function (context = globalThis) { // 关键步骤,在 context 上调用方法,触发 this 绑定为 context context.fn = this; let args = [].slice.call(arguments, 1); let res = context.fn(...args); delete context.fn; return res; };复制代码
Function.prototype.myApply = function (context = globalThis) { // 关键步骤,在 context 上调用方法,触发 this 绑定为 context context.fn = this; let res; if (arguments[1]) { res = context.fn(...arguments[1]); } else { res = context.fn(); } delete context.fn; return res; };复制代码
function deepCopy(obj, cache = new WeakMap()) { if (!obj instanceof Object) return obj; // 防止循环引用 if (cache.get(obj)) return cache.get(obj); // 支持函数 if (obj instanceof Function) { return function () { obj.apply(this, arguments); }; } // 支持日期 if (obj instanceof Date) return new Date(obj); // 支持正则对象 if (obj instanceof RegExp) return new RegExp(obj.source, obj.flags); // 还可以增加其他对象,比如:Map, Set等,根据情况判断增加即可,面试点到为止就可以了 // 数组是 key 为数字素银的特殊对象 const res = Array.isArray(obj) ? [] : {}; // 缓存 copy 的对象,用于出来循环引用的情况 cache.set(obj, res); Object.keys(obj).forEach((key) => { if (obj[key] instanceof Object) { res[key] = deepCopy(obj[key], cache); } else { res[key] = obj[key]; } }); return res; }复制代码
class EventEmitter { constructor() { this.cache = {}; } on(name, fn) { if (this.cache[name]) { this.cache[name].push(fn); } else { this.cache[name] = [fn]; } } off(name, fn) { const tasks = this.cache[name]; if (tasks) { const index = tasks.findIndex((f) => f === fn || f.callback === fn); if (index >= 0) { tasks.splice(index, 1); } } } emit(name) { if (this.cache[name]) { for (let fn of this.cache[name]) { fn(); } } } emit(name, once = false) { if (this.cache[name]) { // 创建事件副本,如果回调函数内继续注册相同事件,触发时,会造成死循环 const tasks = this.cache[name].slice() for (let fn of tasks) { fn(); } if (once) { delete this.cache[name] } } } }复制代码
function curry(func) { return function curried(...args) { if (args.length >= func.length) { func.apply(this, args); } else { return function (...args2) { curried.apply(this, args.concat(args2)); }; } }; }复制代码
function create(proto) { function F() {} F.prototype = proto; return new F(); }// Parentfunction Parent(name) { this.name = name; } Parent.prototype.say = function () { console.log(this.name); };// Childfunction Child(age, name) { Parent.call(this, name); this.age = age; } Child.prototype = create(Parent.prototype); Child.prototype.constructor = Child; Child.prototype.say = function () { console.log(this.age); };复制代码
function instanceOf(instance, klass) { let proto = instance.__proto__; let prototype = klass.prototype; while (true) { if (proto === null) return false; if (proto === prototype) return true; proto = proto.__proto__; } }复制代码
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