How do I merge two arrays to create one array in JavaScript?

Question

Imagine I've got two arrays in JavaScript:

var geoff = ['one', 'two'];
var degeoff = ['three', 'four'];

How do I merge the two arrays, resulting in an array like this?

var geoffdegeoff = ['one', 'two', 'three', 'four'];

molf · Accepted Answer · 2009-08-26 16:20:18Z

15

var geoffdegeoff = geoff.concat(degeoff);

answered Aug 26, 2009 at 16:20

molf

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Comments

james emanon · Accepted Answer · 2013-08-26 04:39:50Z

3

I stumbled across this and thought to add an additional way.

note: I see you want to create a third new var.

.concat is good, but you have to create a new array (unless you override the orig).

How about if you want to merge/combine array "second" into array "first".

Here is a nifty way.

// using apply
var first = ['aa','bb','cc'];
var second = ['dd','ee'];
first.push.apply(first, second);
first;

or

Array.prototype.push.apply(first, second); 
first;

answered Aug 26, 2013 at 4:39

james emanon

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Array.prototype == [] :)

I get what you are saying, but by passing in "first" as "this", we are changing/applying the second in place. I hope I get what you mean. lol.

I don't think you actually got my point; [].push.apply(first, second) is what I mean :)

This will be useful for big arrays, whereby truly appending data prevents a full array copy.

@Jack: While the substitution is valid in this case, Array.prototype != [].

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