JavaScript数组去重

1. Set配合扩展操作符…或Array.from

var arr = [1,1,2,2,3,4,4];var set = new Set(arr);  //Set(4) {1, 2, 3, "a"}var newArr = [...set];//(4) [1, 2, 3, 4],...扩展操作符内部用for of实现var newArr2 = Array.from(set);//(4) [1, 2, 3, 4]({}).toString.call(set); //"[object Set]"

2. filter

arr.filter(function(value,index,arr){    return arr.indexOf(value) === index;});