003-ES6常用语法

ES6常用语法

• let、const
• 模板字符串
• 属性简写、方法简写
• 箭头函数
• promise
• async、await
• 解构赋值
• import、export
• 扩展运算符

let、const

💡 Tips：不可重复声明，const不可改，块级作用域限制

let name1 = 'zhangsan';
const AGE = 10;

模板字符串

const info = `my name is ${name1}, i am ${AGE}`;

属性简写、方法简写

const obj1 = {
  name1,
  run() {
    console.log('i can run !');
  },
};

箭头函数

const arr = [1, 2, 3, 4];
arr.forEach((item, i) => {
  console.log(`arr索引为：${i}, 值为：${item}`);
});

promise

💡 Tips：解决回调地狱，异步请求

const p = new Promise((resolve, reject) => {
  setTimeout(() => {
    if (Math.random() > 0.5) {
      resolve('succeed');
    } else {
      reject('failed');
    }
  }, 3000);
});
p.then(res => {
  console.log('promise success --', res);
}).catch(err => {
  console.log('promise fail --', err);
});

async、await

💡 Tips：对 promise 的优化写法，更清晰

function main() {
  return new Promise((resolve, reject) => {
    setTimeout(() => {
      console.log('main 内部方法');
      resolve('main 执行成功');
    }, 3000);
  });
}

async function getMain() {
  const data = await main();
  console.log('getMain 方法执行', data);
}
getMain();
console.log('外部方法');

解构赋值

let { name, age } = {
  name: 'zhangsan',
  age: 12,
};
let [arr1, arr2] = [2, 3];

import、export

import { mapMutations } from 'vuex';

export const fn = (data) => {};

扩展运算符

💡 Tips：对象合并

const obj = {
  name: 'zhangsan',
  age: 19,
};

const obj3 = {
  ...obj,
  age: 10,
};