es6

set：会去重

var arr=["1","1","2"]; //长度为3

var list =new Set(["sun","sun","git","svn"])  //长度为3

console.log(list.size);//3

list.delete("svn")  //true

list.delete("abc")  //false

list.has("sun")  //true

list.add("test")  //在后面添加成功

list.clear(); //清空后length=0

let title = "我是标题";
let tpl = `测试:${title}`  

//tpl 的值为："测试:我是标题"

新增的方法：

"helloworld".includes('Y') //false

"hellworld".startsWith('s')  //false

"hellworld".endsWith('d')  //true 注意区分大小写


"hao ".repeat(10) //"hao hao hao hao hao hao hao hao hao hao "


let[a,b,c]="nih"

console.log(a)  //  n
console.log(b)  //  i
console.log(c)   //  h


let {length} ="sdfsdfsdf";
//length长度为：9


let {floor,pow}=Math;
let a=1.9;
console.log(floor(a));

变量的解构和复制(好早之前写的了，没测试，先放着)

//var obj={
// a:1,
// b:2
//}

//let a = 0;
//({ a, b } = obj);
//console.log(a)
//console.log(b)



//let {a:A,b}=obj;
//console.log(A)
//console.log(b)


//let { a,b }=obj;

//console.log(a)
//console.log(b)


//let { c,b }=obj;
//console.log(c) //undefined









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



//let [a,b,c]=[1,2];
//c会变成undefined




//es6 解构赋值数组
//var [a,b,c='default',d='default'] = [1,2,3];
//console.log(a)
//console.log(b)
//console.log(c)
//console.log(d)



//let 一个方法 代码域

//if (true) {
// var a = 1;
// let b = 2;
//}

//console.log(a);
//console.log(b); //会报错



//var a = 1;

//function foo() {

// if (false) {

// var a = 2;
// }

// console.log(a); //a 会变成undefined
//}

//foo()



//console.log(a);//a 会变成undefined
//var a;