数组去重的方式有很多种，现总结一些备以后查漏补缺来用。

对基本数组类型去重：

（1）set 和 array.from()实现

var str,    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat(arr) {   return  Array.from(new Set(arr))}console.log(removeRepeat(strs)) //["a", "b", "c", "er", "d"]

（2） indexOf和forEach()

var str=[],    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat() {  strs.forEach(v=>{    if(str.indexOf(v) < 0) str.push(v)  })  console.log(str) //["a", "b", "c", "er", "d"]}

（3）map 和 filter

var str=[],    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat(arr) {  const unique = new Map()  return arr.filter(v=>{    return !unique.has(v) && unique.set(v,1)  })} console.log(removeRepeat(strs)) //["a", "b", "c", "er", "d"]

延伸1：需要对数组排序去重

var str=[],    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat(arr) { let arry = arr.sort() return arr.sort().filter((v,index) => {   return !index || v !== arry[index-1] })}console.log(removeRepeat(strs))//  ["a", "b", "c", "d", "er"]

延伸2：某一个元素只出现一次

（1）利用filter，indexof，lastIndexOf对基本类型数组去重复元素

var str,    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat() {    str = strs.filter(function (value, index, array) {        return array.indexOf(value) === array.lastIndexOf(value);    })    console.log(str) //["d"]}

（2）利用lastIndexOf，splice对基本类型数组去重复元素

var str,    strs = ['a', 'b', 'c', 'er', 'd', 'er', 'a', 'b', 'c'];function removeRepeat() {    for (var i = 0; i < strs.length; i++) {        if (i !== strs.lastIndexOf(strs[i])) strs.splice(i, 1);    }    console.log(str) //["d"]}

（1）和（2）的方法大同小异，原理是一样

延伸3：对数组对象进行去重

var Messages = [    {        "timestamp": 1474328370007,        "message": "hello"    },    {        "timestamp": 1474328302520,        "message": "how are you"    },    {        "timestamp": 1474328370007,        "message": "hello"    },    {        "timestamp": 1474328370007,        "message": "hello"    }]var NoRepeatMessages = [];function RemoveRepeat(arr) {    var hashFlag = {}    arr.forEach((v,index) => {        if (!hashFlag[v.timestamp]) {            hashFlag[v.timestamp] = true;            NoRepeatMessages.push(v);        }    });  console.log(NoRepeatMessages) //[{"timestamp": 1474328370007,"message": "hello"},{ "timestamp": 1474328302520,"message": "how are you"}]}RemoveRepeat(Messages)