虽然ES6解决方案是最好的，但我很困惑，没有人展示了以下解决方案：

function removeDuplicates(arr){
    o={}
    arr.forEach(function(e){
        o[e]=true
    })
    return Object.keys(o)
}

这里需要记住的是，对象必须具有唯一的键。我们正在利用这一点来删除所有重复项。我本以为这是最快的解决方案（在ES6之前）。

请记住，这也会对数组进行排序。

删除字符串重复项的最简单方法是使用关联数组，然后遍历关联数组以使列表/数组返回。

如下所示：

var toHash = [];
var toList = [];

// add from ur data list to hash
$(data.pointsToList).each(function(index, Element) {
    toHash[Element.nameTo]= Element.nameTo;
});

// now convert hash to array
// don't forget the "hasownproperty" else u will get random results 
for (var key in toHash)  {
    if (toHash.hasOwnProperty(key)) { 
      toList.push(toHash[key]);
   }
}

瞧，现在复制品不见了！

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);

对thg435的优秀答案稍作修改，以使用自定义比较器：

function contains(array, obj) {
    for (var i = 0; i < array.length; i++) {
        if (isEqual(array[i], obj)) return true;
    }
    return false;
}
//comparator
function isEqual(obj1, obj2) {
    if (obj1.name == obj2.name) return true;
    return false;
}
function removeDuplicates(ary) {
    var arr = [];
    return ary.filter(function(x) {
        return !contains(arr, x) && arr.push(x);
    });
}

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"]);

$(document).ready(function() {

    var arr1=["dog","dog","fish","cat","cat","fish","apple","orange"]

    var arr2=["cat","fish","mango","apple"]

    var uniquevalue=[];
    var seconduniquevalue=[];
    var finalarray=[];

    $.each(arr1,function(key,value){

       if($.inArray (value,uniquevalue) === -1)
       {
           uniquevalue.push(value)

       }

    });

     $.each(arr2,function(key,value){

       if($.inArray (value,seconduniquevalue) === -1)
       {
           seconduniquevalue.push(value)

       }

    });

    $.each(uniquevalue,function(ikey,ivalue){

        $.each(seconduniquevalue,function(ukey,uvalue){

            if( ivalue == uvalue)

            {
                finalarray.push(ivalue);
            }   

        });

    });
    alert(finalarray);
});