https://jsfiddle.net/2w0k5tz8/

function remove_duplicates(array_){
    var ret_array = new Array();
    for (var a = array_.length - 1; a >= 0; a--) {
        for (var b = array_.length - 1; b >= 0; b--) {
            if(array_[a] == array_[b] && a != b){
                delete array_[b];
            }
        };
        if(array_[a] != undefined)
            ret_array.push(array_[a]);
    };
    return ret_array;
}

console.log(remove_duplicates(Array(1,1,1,2,2,2,3,3,3)));

循环、删除重复项并创建克隆数组占位符，因为不会更新数组索引。

向后循环以获得更好的性能（循环不需要一直检查阵列的长度）

这里是另一种使用jQuery的方法，

function uniqueArray(array){
  if ($.isArray(array)){
    var dupes = {}; var len, i;
    for (i=0,len=array.length;i<len;i++){
      var test = array[i].toString();
      if (dupes[test]) { array.splice(i,1); len--; i--; } else { dupes[test] = true; }
    }
  } 
  else {
    if (window.console) console.log('Not passing an array to uniqueArray, returning whatever you sent it - not filtered!');
      return(array);
  }
  return(array);
}

作者：William Skidmore

在ECMAScript 6（又名ECMAScript2015）中，Set可用于过滤重复项。然后可以使用扩展运算符将其转换回数组。

var names = ["Mike","Matt","Nancy","Adam","Jenny","Nancy","Carl"],
    unique = [...new Set(names)];

选择这个：

var uniqueArray = duplicateArray.filter(function(elem, pos) {
    return duplicateArray.indexOf(elem) == pos;
}); 

现在uniqueArray不包含重复项。

以下脚本返回仅包含唯一值的新数组。它适用于字符串和数字。不需要额外的库，只需要普通的JS。

浏览器支持：

Feature Chrome  Firefox (Gecko)     Internet Explorer   Opera   Safari
Basic support   (Yes)   1.5 (1.8)   9                   (Yes)   (Yes)

https://jsfiddle.net/fzmcgcxv/3/

var duplicates = ["Mike","Matt","Nancy","Adam","Jenny","Nancy","Carl","Mike","Mike","Nancy","Carl"]; 
var unique = duplicates.filter(function(elem, pos) {
    return duplicates.indexOf(elem) == pos;
  }); 
alert(unique);

var duplicates = function(arr){
     var sorted = arr.sort();
   var dup = [];
   for(var i=0; i<sorted.length; i++){
        var rest  = sorted.slice(i+1); //slice the rest of array
       if(rest.indexOf(sorted[i]) > -1){//do indexOf
            if(dup.indexOf(sorted[i]) == -1)    
         dup.push(sorted[i]);//store it in another arr
      }
   }
   console.log(dup);
}

duplicates(["Mike","Matt","Nancy","Adam","Jenny","Nancy","Carl"]);