es6语法小结 - 爱码网

1、解构赋值

数组：

let arr=[1,2,3];let [a,b,c]=arr;

console.log(a);//1

let arr2=[1,2,3];let [a,...b]=arr2;

console.log(a);//1

console.log(b.length);//2个

console.log(b);//相当于剩余项值为[2,3]

对象：

obj={a: 10, b: 20, c: 30, d: 40};

let {a, b, ...rest} = obj;

console.log(a);//10

console.log(b);//20

console.log(rest);//相当于剩余项值为{c: 30, d: 40}

应用示例如图所示：

function add(...values) { let sum = 0; for (var val of values) { sum += val; } return sum; }

add(2, 5, 3) // 10

function add(x, y) { return x + y; } var numbers = [4, 38]; add(...numbers) // 42

// ES5 [1, 2].concat(more)

// ES6 [1, 2, ...more]

// ES5的合并数组 arr1.concat(arr2, arr3); // [ 'a', 'b', 'c', 'd', 'e' ]

// ES6的合并数组 [...arr1, ...arr2, ...arr3] // [ 'a', 'b', 'c', 'd', 'e' ]

es6语法小结

二、对象赋值合并

var o1 = {a: 1}; var o2 = {b: 2}; var o3 = {c: 3};

var obj = Object.assign(o1, o2, o3);

console.log(obj); //{a: 1, b: 2, c: 3}

console.log(o1); //{a: 1, b: 2, c: 3}, 目标对象o1被改变了

三、箭头函数及foreach遍历、数组过滤filter

var foo = function(){return 1;}; //等价于 let foo = () => 1;

let nums = [1,2,3,5,10]; let fives = []; nums.forEach(v => { if (v % 5 === 0) fives.push(v); }); console.log(fives); //[5,10]

var ages = [32, 33, 16, 40];

var newAges= ages.filter(age=> age>18);//[32,33,40]

注意(v)中括号可以省略，只有一个值时；

四、模板字符串

let name = "Bob", time = "today";

`Hello ${name}, how are you ${time}?`

es6语法小结

let str="hahav";
console.log(str.includes('a'));//true,真判断是否存在方式一
console.log(str.indexOf('a'));//4,>0判断是否存在方式二

参考es6地址

es6语法小结