es6零碎知识点整理-白红宇

module

components/HelloWorld.vue

import { a } from "@/modules";import b from "@/modules";export default {  mounted() {    console.log(a);    b();  }};复制代码

modules/index.js

let a = 'JonSnow'let b = 'Cercei'export {    a}export default () => console.log(b);复制代码

components/HelloWorld.vue

import b from "@/module";export default {  mounted() {    b().then(res => {      console.log(res);    });  }};复制代码

modules/index.js

export default () => new Promise((resolve, reject) => {    setTimeout(() => {    	resolve('es6 module')    }, 200)})复制代码

class

class Person {  constructor(name, age) {    this.name = name;    this.age = age;  }  say() {    console.log(`${
     this.name}'s age is ${
     this.age}`);  }}class Student extends Person {  constructor(name, age, sex) {    super(name, age);    this.sex = sex;  }  saySex() {    console.log(      `${
     this.name}'s age is ${
     this.age} and his sex is ${
     this.sex}`    );  }}let JonSnow = new Student("JonSnow", 21, "男");JonSnow.say();JonSnow.saySex();console.log(JonSnow);console.log(JonSnow instanceof Student);console.log(JonSnow instanceof Person);复制代码

includes && indexOf

let arr = [1, 2, 3];console.log(arr.includes(1));console.log(arr.indexOf(100));复制代码

全局作用域与函数作用域

var a = 12;function fn() {  console.log(a);  var b = 13;  if (true) {    var c = 14;    console.log(b);  }  console.log(c);}fn();console.log(c);//报错复制代码

函数执行完后，变量就被销毁了

使用undefined传参

function myFunction(x = 1, y = 2, z = 3) {  console.log(x, y, z);//1,7,9}myFunction(undefined, 7, 9);复制代码

参数运算

function myFunction(x, y, z = x + y) {  console.log(x, y, z);//1,2,3}fn(1, 2);复制代码

push

let a1 = [1];let a2 = [2, 3, 4];// a1.push(2, 3, 4);a1.push(...a2);console.log(a1);复制代码

忽略数组中的某些值

let [a, , b] = [1, 2, 3];console.log(a); //1console.log(b); //3复制代码

使用展开语法

let [a, ...b] = [1, 2, 3];console.log(a); // 1console.log(b); //[2,3]复制代码

let [a, , ...b] = [1, 2, 3, 4, 5];console.log(a); //1console.log(b); //[3,4,5]复制代码

let [a, b, c = 3] = [1, 2];console.log(a); //1console.log(b); //2console.log(c); //3复制代码

function myFunction([a, b, c = 3] = [1, 2, 3]) {  console.log(a, b, c);//1 2 3}myFunction();复制代码

function myFunction([a, b, c = 3] = [1, 2, 3]) {  console.log(a, b, c);//1 2 3}myFunction(undefined);复制代码