Get all unique values in a JavaScript array (remov

Question

I have an array of numbers that I need to make sure are unique. I found the code snippet below on the internet and it works great until the array has a zero in it. I found this other script here on SO that looks almost exactly like it, but it doesn't fail.

So for the sake of helping me learn, can someone help me determine where the prototype script is going wrong?

Array.prototype.getUnique = function() {
 var o = {}, a = [], i, e;
 for (i = 0; e = this[i]; i++) {o[e] = 1};
 for (e in o) {a.push (e)};
 return a;
}

More answers from duplicate question:

• Remove Duplicates from JavaScript Array

Similar question:

• Get all values with more than one occurrence (i.e.: not unique) in an array

Answer 1

Simplest solution:

var arr = [1, 3, 4, 1, 2, 1, 3, 3, 4, 1];
console.log([...new Set(arr)]);

Or:

var arr = [1, 3, 4, 1, 2, 1, 3, 3, 4, 1];
console.log(Array.from(new Set(arr)));

Answer 2

To address the problem the other way around, it may be useful to have no duplicate while you load your array, the way Set object would do it but it's not available in all browsers yet. It saves memory and is more efficient if you need to look at its content many times.

Array.prototype.add = function (elem) {
   if (this.indexOf(elem) == -1) {
      this.push(elem);
   }
}

Sample:

set = [];
[1,3,4,1,2,1,3,3,4,1].forEach(function(x) { set.add(x); });

Gives you set = [1,3,4,2]

Answer 3

This prototype getUnique is not totally correct, because if i have a Array like: ["1",1,2,3,4,1,"foo"] it will return ["1","2","3","4"] and "1" is string and 1 is a integer; they are different.

Here is a correct solution:

Array.prototype.unique = function(a){
    return function(){ return this.filter(a) }
}(function(a,b,c){ return c.indexOf(a,b+1) < 0 });

using:

var foo;
foo = ["1",1,2,3,4,1,"foo"];
foo.unique();

The above will produce ["1",2,3,4,1,"foo"].

Answer 4

Without extending Array.prototype (it is said to be a bad practice) or using jquery/underscore, you can simply filter the array.

By keeping last occurrence:

    function arrayLastUnique(array) {
        return array.filter(function (a, b, c) {
            // keeps last occurrence
            return c.indexOf(a, b + 1) < 0;
        });
    },

or first occurrence:

    function arrayFirstUnique(array) {
        return array.filter(function (a, b, c) {
            // keeps first occurrence
            return c.indexOf(a) === b;
        });
    },

Well, it's only javascript ECMAScript 5+, which means only IE9+, but it's nice for a development in native HTML/JS (Windows Store App, Firefox OS, Sencha, Phonegap, Titanium, ...).

Answer 5

Using object keys to make unique array, I have tried following

function uniqueArray( ar ) {
  var j = {};

  ar.forEach( function(v) {
    j[v+ '::' + typeof v] = v;
  });


  return Object.keys(j).map(function(v){
    return j[v];
  });
}   

uniqueArray(["1",1,2,3,4,1,"foo", false, false, null,1]);

Which returns ["1", 1, 2, 3, 4, "foo", false, null]

Answer 6

You can also use underscore.js.

console.log(_.uniq([1, 2, 1, 3, 1, 4]));

<script src="http://underscorejs.org/underscore-min.js"></script>

which will return:

[1, 2, 3, 4]