ES6之Set对象作用

1、数组去重

var mySet = new Set([1, 2, 3, 4, 4]);
[...mySet];     // [1, 2, 3, 4]

2、并集

var a = new Set([1, 2, 3]);
var b = new Set([4, 3, 2]);
var union = new Set([...a, ...b]); 
console.log(union);     // {1, 2, 3, 4}

3、交集

var a = new Set([1, 2, 3]);
var b = new Set([4, 3, 2]);
var intersect = new Set([...a].filter(x => b.has(x))); 
console.log(intersect)     // {2, 3}

4、差集

var a = new Set([1, 2, 3]);
var b = new Set([4, 3, 2]);
var difference1 = new Set([...a].filter(x => !b.has(x))); 
console.log(difference1)     // a与b的差集是{1}
var difference2 = new Set([...b].filter(x => !a.has(x))); 
console.log(difference2)     // a与b的差集是{4}
var difference3 =new Set([...[...a].filter(x => !b.has(x)),...[...b].filter(x => !a.has(x))]);     
console.log(difference3)      // {1,4}