Array数组去重

1.循环方法

function methodOne(arr){
    var result = [],
        arrLen = arr.length,
        item   = null,
        i,j;
    for(var i = 0; i < arrLen; i++){            //循环数组长度
        item = arr[i];                          //当前项
        var resultLen = result.length;          //新建数组长度
        for(var j = 0; j < resultLen; j++){     //循环新数组
            if(item === result[j]){             //如果当前item等新数组中的其中一个就跳过;
                break;                          //停止循环
            }
        }
        if(j === resultLen){                    //如果长度相等就添加当前项
            result.push(item);
        }
    }
    return result;
}

2.数组的indexOf()方法,需要做IE兼容

function methodTwo(arr){
    var result = [];
    var arrLen = arr.length;
    var item,i;
    for(var i = 0; i < arrLen; i++){
        item = arr[i];
        if(result.indexOf(item) === -1){     //如果不存在就添加
            result.push(item);
        }
    }
    return result;
}
//添加数组IndexOf方法
if (!Array.prototype.indexOf){
    Array.prototype.indexOf = function(elt /*, from*/){
        var len = this.length >>> 0;
        var from = Number(arguments[1]) || 0;
        from = (from < 0) ? Math.ceil(from) : Math.floor(from);
        if (from < 0){
            from += len;
        }

        for (; from < len; from++){
            if (from in this && this[from] === elt){
                return from;
            }
        }
        return -1;
    };
}

3.ES5方法的forEach()方法

function methodThree(arr){
    var result = [];
    //三个参数:数组元素,元素的索引,数组本身
    arr.forEach(function(item,index,array){
        //从前面开始查找数组中的元素,如果有重复的,查找的索引与元素索引不相等
        if(array.indexOf(item) === index){
            result.push(item);
        }
    })
    return result;
}

4.判断类型(能去除个对象组成的数组)

function methodFive(arr){
    var result = [];
    var hash = [];
    var len = arr.length;
    for(var i = 0; i < len; i++){
        var item = arr[i];
        var key;
        key = typeof(item) + item;          //判断类型+值
        if(typeof(item) === "object"){      //多个对象时
            for(var j in item){             //循环键值对
                key = item[j];              //判断类型+值
            }
        }
        if(hash[key] !== 1){                //如果没有此类型+值,则添加,并将hash[key]赋值为1,如果有重复,下次就有值了
            result.push(item);
            hash[key] = 1;
        }
    }
    return result;
}

5.对象的重写覆盖特性(最快的)

Array.prototype.unique = function(){
    var obj = {},
        len = this.length,
        result = [],
        i;
    for(i = 0; i < len; i++){
        var item = this[i];
        obj[item] = item;       //obj[this[i]]得属性值,如有相同值就会覆盖重写了
    }
    for(i in obj){
        result.push(obj[i]);
    }
    return result;
}

另一种函数定义方法(以上同理)

function eliminateDuplicates(arr){
    var i,
        len = arr.length,
        result = [],
        obj = {};
    for(var i = 0; i < len; i++){
        obj[arr[i]] = 0;
    }
    for(i in obj){
        result.push(i);
    }
    return result;
}

测试

var arr1 = [5,7,3,1,7,5,6];
var arr2 = [8,9,5,9,8,3,"3",1];
var arr3 = ["q","b","a","o","q","a"];
var arr4 = ["a","b","c","a","a"];
var arr5 = [{name:"xiaoma"},1,"a",{id:"xl"}];
var arr6 = [{name:"xiaoma"},{name:"xiaoma"}];
var arr7 = [{name:"xiaoma",id:5},{name:"xiaoma2",id:6},{name:"xiaoma3",id:5}];
var arr8 = [true,false,false,true];
var arr9 = [/[\d]/,/[\w]/];
var arr10 = [/[\d]/,/[\d]/];