var daObj = {
get val() {
return ;
},
set val(value) {
}
}复制代码
get:
var da = { a: 1,
get val(){ return this.a + 1;
}
}console.log(da.val);//2da.val = 100;console.log(da.val);//2class Da { constructor(type) { this.type = type
}
get age() { return 1
}
set age(val) { this.realAge = val
}
eat() { console.log('i am eat')
}
}let da1 = new Da('da1')console.log(da1.age)
da1.age = 1console.log(da1.realAge)复制代码
class Da {
constructor(type, age) {
this.type = type
this.age1 = age
}
get age() {
return this._age
}
set age(val) {
this._age = val
}
}复制代码
利用set/get实现对element.innerHTML封装
class myHTMLElement {
constructor(element) {
this.element = element
}
get html() {
return this.element.innerHTML
}
set html(value) {
this.element.innerHTML = value
}
}复制代码
设置一个闭包，通过一定的规则来限制对它的修改：
let myName = 'dada'
class Da {
constructor(type) {
this.type = type
}
get name() {
return myName
}
set name(val) {
myName = val
}
}复制代码
4.静态方法
在es5中实现的静态方法：
let Da = function (type) { this.type = type this.eat = function() { console.log('i eat')
}
}
Da.study = function(book) { console.log('i book');
}复制代码
let Da = function(type) { this.type = type
}
Da.prototype.eat = function() {
Da.walk() console.log('i am')
}
Da.walk = function(){ console.log('walk')
}let da1 = new Da('da1')
da1.eat()// walk// i am复制代码
静态方法在你的实例化对象是找不到的
在es6中的静态方法，标记static
class Da {
constructor(type) {
this.type = type
}
eat() {
console.log('i eat')
}
static study() {
console.log('i study')
}
}复制代码
class Da { constructor(type) { this.type = type
}
eat() { // Da.walk();
console.log('i eat')
} static walk(){ console.log('i walk')
}
}class da extends Da { // 构造函数
//constructor (type) {
//super(type)
//}
run() { console.log('i run')
}
}let da1 = new da('da1')复制代码
6.面向对象编程Class
类的声明，属性，方法，静态方法，继承，多态，私有属性
// 类的声明
let Da = function(type) {
this.type = type
this.eat = function() {
console.log('i eat');
}
}
let da = new Da('da');复制代码
// prototype
let Da = function(type) {
this.type = type
}
Da.prototype.eat = function() {
console.log('i eat')
}
let da1 = new Da('da1')复制代码
es6中的Class
class Da {
// 构造函数
constructor(type) {
this.type = type
}
// 方法
walk() {
console.log('i walk')
}
}
let da = new Da('da');
// console.log(typeof Da); function复制代码
7.函数参数的默认值
函数参数是从左到右解析，如果没有默认值会被解析成 undefined
// 参数默认值
function da (x,y,z) {
}
function sum() {
let num = 0
Array.prototype.forEach.call(arguments, function(item){
num += item * 1
})
Array.from(arguments).forEach(function(item){
num += item * 1
})
return num
}复制代码
// 不确定
function sum(...nums) {
let num = 0
nums.forEach(function(item){
num += item * 1
})
return num
}
console.log(sum(1,2,3,4,5))复制代码
function sum () {
let num = 0
Array.prototype.forEach.call(arguments, function (item) {
num += item * 1
})
return num
}
function sum (...nums) {
let num = 0
nums.forEach(function (item) {
num += item * 1
})
return num
}复制代码
let set = new Set([1, 2, 3, 4, 4]);
// 添加数据
let addSet = set.add(5);
console.log(addSet); // Set(5) {1, 2, 3, 4, 5}
// 删除数据
let delSet = set.delete(4);
console.log(delSet); // true
// 查看是否存在数据 4
let hasSet = set.has(4);
console.log(hasSet); // false
// 清除所有数据
set.clear();
console.log(set); // Set(0) {}复制代码
实现并集（Union）、交集（Intersect）和差集（Difference）
let a = new Set([1, 2, 3]);
let b = new Set([4, 3, 2, 1]);
// 并集
let union = new Set([...a, ...b]);
// Set {1, 2, 3, 4}
// 交集
let intersect = new Set([...a].filter(x => b.has(x)));
// set {1, 2, 3}
// 差集
let difference = new Set([...b].filter(x => !a.has(x)));
// Set {4}复制代码
12.Map数据结构
JS当中的哈希表，使用方法如下：
let map = new Map()
map.set(1, 2)
map.set(3, 4)
map.set(1, 3)
console.log(map)
创建
var da = new Map();
var jeskson = {};
遍历
da.forEach(function(value,key,map){}
长度
da.size
删除
//da.delete() 删除key，全部清楚da.clear()
新增
da.set(key,value)
da.has(查索引值)
da.forEach((value,key) =>{
})
for( let [key, value] of map){}
// let map = new Map( [[1,2], [3,4]] )
map的key任意都可以
let o = function() {
console.log('o')
}
map.set(o, 3)
console.log(map.get(o)); // 3复制代码
var myArray = ['a', 'b', 'c'];var
one = myArray[0],
two = myArray[1],
three = myArray[2];// one = 'a', two = 'b', three = 'c'复制代码
ES6解构允许使用更简单方法：
const [one, , three] = myArray;// one = 'a', three = 'c'复制代码
使用rest运算符（...）提取剩余元素：
const [one, ...two] = myArray;// one = 'a', two = ['b, 'c']复制代码
const myObject = { one: 'a', two: 'b', three: 'c'};// ES6 destructuring exampleconst {one: first, two: second, three: third} = myObject;// first = 'a', second = 'b', third = 'c'复制代码
可变值交换
var a = 1, b = 2;// ES5 swapvar temp = a;
a = b;
b = temp;// a = 2, b = 1// ES6 swap back[a, b] = [b, a];// a = 1, b = 2[b, c, d, e, a] = [a, b, c, d, e];复制代码
在ES6中，我们可以为任何参数分配默认值
function dada(param = {}) {复制代码
函数返回多个值（函数只能返回一个值，但可以是一个复杂的对象或多维数组）
function f() { return [1, 2, 3];
}const [a, b, c] = f();// a = 1, b = 2, c = 3复制代码
ES6 JavaScript深度解构
默认情况下，找不到的属性为undefined
var {da} = {bar: 'dada'}console.log(da)// undefined复制代码
如果访问不存在的父级的深层嵌套属性，则将获得异常。
var {da:{bar}} = {dada: 'dadaqianduan'}// Exception复制代码
var person = { name: "dada", age: 17};
person = new Proxy(person, {
set(target, property, value) { if (value === 18) { console.log("Congratulations! You are of legal age"); Reflect.set(target, property, value); return true;
}
}
});
person.age = 18;if (value < 13 && value > 99) { throw new Error('The age should be between 13 and 99')
} else { Reflect.set(target, property, value)
}复制代码
导出变量或者常量
export const da = 'dadaqianduan'
export let da1 = 'da1'
export var da2 = 'da1'
const name = 'dada'
let name1 = 'dada1'
export {
name,
name1
}
导出函数
export function da(value){
console.log(value)
}
const da = (value) => {
console.log(value);
}
export {
da
}
导出Object
export({
name: 'da1',
message: 'dadaqianduan'
})
let da = {
name: 'name1'
}
export {
da
}
导出Class
class Da {
constructor(){
this.id = 1
}
}
export {
Da
}
export class Da {
constructor() {
this.id = 1
}
}
修改导出名称
const name = 'da1'
export {
name as cname
}
export default name复制代码
import
// 直接导入
const name = 'dada'
let name1 = 'dada1'
var name2 = 'dada2'
export {
name as cname
}
export default name2
import name2, {name1, name} from A复制代码
export const sqrt = Math.sqrt;
export function square(x) {
return x * x;
}
export function dada(x,y) {
return sqrt(square(x) + square(y));
}
import {square,da} from 'da';
console.log(square(11)); // 121
console.log();复制代码
export default function() {...}
import myFunc from 'myFunc';
export default class{...}
import MyClass from 'MyClass';
const inst = new MyClass();复制代码
20.import, export
require
--lib.js--
function add(x,y){
return x + y
}
module.exports = {
add: add,
};
--main.js--
var add = require('lib').addd;
console.log(add(1,2));复制代码
import
--lib.js--
export function add(x,y) {
return x + y
}
--main.js--
import {add} from 'lib';
console.log(add(1,2));复制代码
--lib.js--
export const sqrt = Math.sqrt;
export function square(x) {
return x * x;
}
export function da(x,y) {
return sqrt(square(x)+square(y));
}
--main.js--
import {square, da} from 'lib'
--myFunc.js--
export default function() {...};
--main.js--
import myFunc from 'myFunc';
myFunc();复制代码
21.Array.prototype.includes,Promise
该方法判断一个数组是否包含一个指定的值，返回布尔值
let da1 = [1,2,3];
console.log(da1.includes(2));复制代码
function da(time) {
return new Promise(function(resolve,reject){
setTimeout(function(){
resolve(time)
},time)
})
}
async function test() {
let arr = [da(2000),da(1000),da(3000)]
for await (let item of arr) {
console.log(Date.now(), item)
}
}复制代码
