数组去重

一.ES6中set方法：[...new Set(arr)]

var arr1 = [1,2,2,3,3,4,5,5];
[...new Set(arr1)].toString()

二.遍历数组，建立新数组，利用indexOf()判断是否存在于新数组中，不存在则push到新数组，最后返回新数组

var arr2 = [1,2,2,2,3,3,4,4,5,5];
function removeSame(arr){
    var ret = [];
    for(var i=0,j=arr.length;i

三.遍历数组，利用object对象保存数组值，判断数组值是否已经保存在object中，未保存则push到新数组并用object[arrayItem]=1的方式记录保存

var arr3 = [1,2,2,2,3,3,4,4,5]
function removeSame(arr){
    var temp = {},ret = [];
    for (var i = 0,j=arr.length;i

四.根据数组下标判断法, 遍历数组，利用indexOf()判断元素的值是否与当前索引相等，如相等则加入

var arr4 = ["apple","apple","orange","orange","banana"]
function removeSame(arr){
    var ret = [];
    arr.forEach(function(ele,index){
        if(arr.indexOf(ele) == index){
            ret.push(ele)
        }
    })
    return ret;
}

五.数组先进行排序，然后比较原数组与新数组，一头一尾进行去重

var arr5 = ["apple","apple","orange","orange","banana"]
function removeSame(arr){
    var ret = [],end;
    debugger;
    arr.sort();   // ["apple","apple","banana","orange","orange",];
    end = arr[0];
    ret.push(arr[0]);
    for(var i = 1; i