Getting a union of two arrays in JavaScript [duplicate]

Solution 1:

With the arrival of ES6 with sets and splat operator (at the time of being works only in Firefox, check compatibility table), you can write the following cryptic one liner:

var a = [34, 35, 45, 48, 49];
var b = [48, 55];
var union = [...new Set([...a, ...b])];
console.log(union);

Little explanation about this line: [...a, ...b] concatenates two arrays, you can use a.concat(b) as well. new Set() create a set out of it and thus your union. And the last [...x] converts it back to an array.

Solution 2:

If you don't need to keep the order, and consider 45 and "45" to be the same:

function union_arrays (x, y) {
  var obj = {};
  for (var i = x.length-1; i >= 0; -- i)
     obj[x[i]] = x[i];
  for (var i = y.length-1; i >= 0; -- i)
     obj[y[i]] = y[i];
  var res = []
  for (var k in obj) {
    if (obj.hasOwnProperty(k))  // <-- optional
      res.push(obj[k]);
  }
  return res;
}

console.log(union_arrays([34,35,45,48,49], [44,55]));

Solution 3:

If you use the library underscore you can write like this

var unionArr = _.union([34,35,45,48,49], [48,55]);
console.log(unionArr);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js"></script>

Ref: http://underscorejs.org/#union

Solution 4:

I'm probably wasting time on a dead thread here. I just had to implement this and went looking to see if I was wasting my time.

I really like KennyTM's answer. That's just how I would attack the problem. Merge the keys into a hash to naturally eliminate duplicates and then extract the keys. If you actually have jQuery you can leverage its goodies to make this a 2 line problem and then roll it into an extension. The each() in jQuery will take care of not iterating over items where hasOwnProperty() is false.

jQuery.fn.extend({
    union: function(array1, array2) {
        var hash = {}, union = [];
        $.each($.merge($.merge([], array1), array2), function (index, value) { hash[value] = value; });
        $.each(hash, function (key, value) { union.push(key); } );
        return union;
    }
});

Note that both of the original arrays are left intact. Then you call it like this:

var union = $.union(array1, array2);

Solution 5:

function unique(arrayName)
{
  var newArray=new Array();
  label: for(var i=0; i<arrayName.length;i++ )
  {  
    for(var j=0; j<newArray.length;j++ )
    {
      if(newArray[j]==arrayName[i]) 
        continue label;
    }
    newArray[newArray.length] = arrayName[i];
  }
  return newArray;
}

var arr1 = new Array(0,2,4,4,4,4,4,5,5,6,6,6,7,7,8,9,5,1,2,3,0);
var arr2= new Array(3,5,8,1,2,32,1,2,1,2,4,7,8,9,1,2,1,2,3,4,5);
var union = unique(arr1.concat(arr2));
console.log(union);