实现一个new的伪代码
function _new(){
let obj = new Object();
let Con = [].shift.call(arguments);
obj.__proto__ = Con.prototype;
let result = Con.apply(obj,arguments);
return typeof result === 'object' ? result : obj
}
深拷贝和浅拷贝
// ----------------------------------------------浅拷贝
// 只是把对象的属性和属性值拷贝到另一个对象中
var obj1 = {
a: {
a1: { a2: 1 },
a10: { a11: 123, a111: { a1111: 123123 } }
},
b: 123,
c: "123"
}
// 方式1
function shallowClone1(o) {
let obj = {}
for (let i in o) {
obj[i] = o[i]
}
return obj
}
// 方式2
var shallowObj2 = { ...obj1 }
// 方式3
var shallowObj3 = Object.assign({}, obj1)
let shallowObj = shallowClone1(obj1);
shallowObj.a.a1 = 999
shallowObj.b = true
console.log(obj1); //第一层的没有被改变，一层以下就被改变了
// ----------------------------------------------深拷贝
// 简易版
function deepClone(o) {
let obj = {}
for (var i in o) {
// if(o.hasOwnProperty(i)){
if (typeof o[i] === "object") {
obj[i] = deepClone(o[i])
} else {
obj[i] = o[i]
}
// }
}
return obj
}
var myObj = {
a: {
a1: { a2: 1 },
a10: { a11: 123, a111: { a1111: 123123 } }
},
b: 123,
c: "123"
}
var deepObj1 = deepClone(myObj)
deepObj1.a.a1 = 999
deepObj1.b = false
console.log(myObj);
// 简易版存在的问题：参数没有做检验，传入的可能是 Array、null、regExp、Date
function deepClone2(o) {
if (Object.prototype.toString.call(o) === "[object Object]") { //检测是否为对象
let obj = {}
for (var i in o) {
if (o.hasOwnProperty(i)) {
if (typeof o[i] === "object") {
obj[i] = deepClone(o[i])
} else {
obj[i] = o[i]
}
}
}
return obj
} else {
return o
}
}
function isObject(o) {
return Object.prototype.toString.call(o) === "[object Object]" || Object.prototype.toString.call(o) === "[object Array]"
}
// 继续升级，没有考虑到数组，以及ES6中的map、set、weakset、weakmap
function deepClone3(o) {
if (isObject(o)) {//检测是否为对象或者数组
let obj = Array.isArray(o) ? [] : {}
for (let i in o) {
if (isObject(o[i])) {
obj[i] = deepClone(o[i])
} else {
obj[i] = o[i]
}
}
return obj
} else {
return o
}
}
// 有可能碰到循环引用问题 var a = {}; a.a = a; clone(a);//会造成一个死循环
// 循环检测
// 继续升级
function deepClone4(o, hash = new map()) {
if (!isObject(o)) return o//检测是否为对象或者数组
if (hash.has(o)) return hash.get(o)
let obj = Array.isArray(o) ? [] : {}
hash.set(o, obj)
for (let i in o) {
if (isObject(o[i])) {
obj[i] = deepClone4(o[i], hash)
} else {
obj[i] = o[i]
}
}
return obj
}
// 递归易出现爆栈问题
// 将递归改为循环，就不会出现爆栈问题了
var a1 = { a: 1, b: 2, c: { c1: 3, c2: { c21: 4, c22: 5 } }, d: 'asd' };
var b1 = { b: { c: { d: 1 } } }
function cloneLoop(x) {
const root = {};
// 栈
const loopList = [ //->[]->[{parent:{a:1,b:2},key:c,data:{ c1: 3, c2: { c21: 4, c22: 5 } }}]
{
parent: root,
key: undefined,
data: x,
}
];
while (loopList.length) {
// 深度优先
const node = loopList.pop();
const parent = node.parent; //{} //{a:1,b:2}
const key = node.key; //undefined //c
const data = node.data; //{ a: 1, b: 2, c: { c1: 3, c2: { c21: 4, c22: 5 } }, d: 'asd' } //{ c1: 3, c2: { c21: 4, c22: 5 } }}
// 初始化赋值目标，key 为 undefined 则拷贝到父元素，否则拷贝到子元素
let res = parent; //{}->{a:1,b:2,d:'asd'} //{a:1,b:2}->{}
if (typeof key !== 'undefined') {
res = parent[key] = {};
}
for (let k in data) {
if (data.hasOwnProperty(k)) {
if (typeof data[k] === 'object') {
// 下一次循环
loopList.push({
parent: res,
key: k,
data: data[k],
})
} else {
res[k] = data[k];
}
}
}
}
return root
}
function deepClone5(o) {
let result = {}
let loopList = [
{
parent: result,
key: undefined,
data: o
}
]
while (loopList.length) {
let node = loopList.pop()
let { parent, key, data } = node
let anoPar = parent
if (typeof key !== 'undefined') {
anoPar = parent[key] = {}
}
for (let i in data) {
if (typeof data[i] === 'object') {
loopList.push({
parent: anoPar,
key: i,
data: data[i]
})
} else {
anoPar[i] = data[i]
}
}
}
return result
}
let cloneA1 = deepClone5(a1)
cloneA1.c.c2.c22 = 5555555
console.log(a1);
console.log(cloneA1);
// ------------------------------------------JSON.stringify()实现深拷贝
function cloneJson(o) {
return JSON.parse(JSON.stringify(o))
}
// let obj = { a: { c: 1 }, b: {} };
// obj.b = obj;
// console.log(JSON.parse(JSON.stringify(obj))) // 报错 // Converting circular structure to JSON
防抖节流
// ---------------------------------------------------------防抖函数
function debounce(func, delay) {
let timeout
return function () {
let arg = arguments
if (timeout) clearTimeout(timeout)
timeout = setTimeout(() => {
func(arg)
}, delay);
}
}
// ---------------------------------------------------------立即执行防抖函数
function debounce2(fn, delay) {
let timer
return function () {
let args = arguments
if (timer) clearTimeout(timer)
let callNow = !timer
timer = setTimeout(() => {
timer = null
}, delay);
if (callNow) { fn(args) }
}
}
// ---------------------------------------------------------立即执行防抖函数+普通防抖
function debounce3(fn, delay, immediate) {
let timer
return function () {
let args = arguments
let _this = this
if (timer) clearTimeout(timer)
if (immediate) {
let callNow = !timer
timer = setTimeout(() => {
timer = null
}, delay);
if (callNow) { fn.apply(_this, args) }
} else {
timeout = setTimeout(() => {
func.apply(_this, arguments)
}, delay);
}
}
}
// ---------------------------------------------------------节流 ，时间戳版
function throttle(fn, wait) {
let previous = 0
return function () {
let now = Date.now()
let _this = this
let args = arguments
if (now - previous > wait) {
fn.apply(_this, arguments)
previous = now
}
}
}
// ---------------------------------------------------------节流 ，定时器版
function throttle2(fn, wait) {
let timer
return function () {
let _this = this
let args = arguments
if (!timer) {
timer = setTimeout(() => {
timer = null
fn.apply(_this, arguments)
}, wait);
}
}
}
call
Function.prototype.myCall = function (context) {
// 先判断调用myCall是不是一个函数
// 这里的this就是调用myCall的
if (typeof this !== 'function') {
throw new TypeError("Not a Function")
}
// 不传参数默认为window
context = context || window
// 保存this
context.fn = this
// 保存参数
let args = Array.from(arguments).slice(1) //Array.from 把伪数组对象转为数组
// 调用函数
let result = context.fn(...args)
delete context.fn
return result
}
apply
Function.prototype.myApply = function (context) {
// 判断this是不是函数
if (typeof this !== "function") {
throw new TypeError("Not a Function")
}
let result
// 默认是window
context = context || window
// 保存this
context.fn = this
// 是否传参
if (arguments[1]) {
result = context.fn(...arguments[1])
} else {
result = context.fn()
}
delete context.fn
return result
}
bind
Function.prototype.myBind = function(context){
// 判断是否是一个函数
if(typeof this !== "function") {
throw new TypeError("Not a Function")
}
// 保存调用bind的函数
const _this = this
// 保存参数
const args = Array.prototype.slice.call(arguments,1)
// 返回一个函数
return function F () {
// 判断是不是new出来的
if(this instanceof F) {
// 如果是new出来的
// 返回一个空对象，且使创建出来的实例的__proto__指向_this的prototype，且完成函数柯里化
return new _this(...args,...arguments)
}else{
// 如果不是new出来的改变this指向，且完成函数柯里化
return _this.apply(context,args.concat(...arguments))
}
}
}
原型继承
var person = {
friends: ["a", "b", "c", "d"]
}
var p1 = Object.create(person)
p1.friends.push("aaa")//缺点：子类的实例共享了父类构造函数的引用属性
console.log(p1);
console.log(person);//缺点：子类的实例共享了父类构造函数的引用属性
组合继承
function Father(name) {
this.name = name
this.hobby = ["篮球", "足球", "乒乓球"]
}
Father.prototype.getName = function () {
console.log(this.name);
}
function Son(name, age) {
Father.call(this, name)
this.age = age
}
Son.prototype = new Father()
Son.prototype.constructor = Son
var s = new Son("ming", 20)
寄生组合继承
function Father(name) {
this.name = name
this.hobby = ["篮球", "足球", "乒乓球"]
}
Father.prototype.getName = function () {
console.log(this.name);
}
function Son(name, age) {
Father.call(this, name)
this.age = age
}
Son.prototype = Object.create(Father.prototype)
Son.prototype.constructor = Son
var s2 = new Son("ming", 18)
网友评论