數組去重

一.ES6中set方法：[...new Set(arr)]

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

二.遍歷數組，創建新數組，利用indexOf()判斷是否存在於新數組中，不存在則push到新數組，最後返回新數組

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<j; i++){
        if(ret.indexOf(arr[i]) === -1){
            ret.push(arr[i])
        }
    }
    return ret;
}

三.遍歷數組，利用object對象保存數組值，判斷數組值是否已經保存在object中，未保存則push到新數組並用object[arrayItem]=1的方式記錄保存

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<j;i++){
        //debugger;
        console.log(temp[arr[i]]);
        if(!temp[arr[i]]){
            temp[arr[i]] = 1;
            ret.push(arr[i])
        }
    }
    return ret;
}

四.根據數組下標判斷法, 遍歷數組，利用indexOf()判斷元素的值是否與當前索引相等，如相等則加入

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.數組先進行排序，而後比較原數組與新數組，一頭一尾進行去重

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<arr.length; i++){
        if(arr[i] != end){
            ret.push(arr[i]);
            end = arr[i];
        }
    }
    return ret;
}