JS数组去重复项的5种方法

1.第一种:数组内逐个对比

Array.prototype.unique1 = function () {
    var r = new Array();
    label:for(var i = 0, n = this.length; i < n; i++) {
        for(var x = 0, y = r.length; x < y; x++) {
            if(r[x] == this[i]) {
                continue label;
            }
        }
        r[r.length] = this[i];
    }
    return r;
}

2.第二种：用正则表达式

Array.prototype.unique2 = function () {
    return this.sort().join(",,").replace(/(,|^)([^,]+)(,,\2)+(,|$)/g,"$1$2$4").replace(/,,+/g,",").replace(/,$/,"").split(",");
}

3.第三种：使用对象的【hasOwnProperty】方法

Array.prototype.unique3 = function() {
    var temp = {}, len = this.length;
    for(var i=0; i < len; i++)  {
        var tmp = this[i];
        if(!temp.hasOwnProperty(tmp)) {
            temp[this[i]] = "my god";
        }
    }
  
    len = 0;
    var tempArr=[];
    for(var i in temp) {
        tempArr[len++] = i;
    }
    return tempArr;
}

4.第四种：先排序，前项比后项

Array.prototype.unique4 = function () {
    var temp = new Array();
      this.sort();
      for(i = 0; i < this.length; i++) {
          if( this[i] == this[i+1]) {
             continue;
        }
        temp[temp.length]=this[i];
      }
      return temp;
}

5.第五种：用hash表

Array.prototype.unique5 = function() {
    var res = [], hash = {};
    for(var i=0, elem; (elem = this[i]) != null; i++)  {
        if (!hash[elem])
        {
            res.push(elem);
            hash[elem] = true;
        }
    }
    return res;
}