Merge values of multiple arrays in object with jQuery or underscore.js

Question

I want to merge values of multiple arrays in one object to one array. For instance:

Object:
  - alpha: Array[3]
     0: "vatG4d6mcjKbpfuAm"
     1: "xkQrKEsfwuYPkDcdz"
     2: "GDg9chZnDGrbLXWGS"
  - bravo: Array[1]
     0: "53LEcQ5MoYXFyvktf"
  - …

The result should be:

["vatG4d6mcjKbpfuAm", "xkQrKEsfwuYPkDcdz", "GDg9chZnDGrbLXWGS", "53LEcQ5MoYXFyvktf"]

I did this with a simple for loop iterating over the elements, but I am concerned about the performance. Is this possible with a simple jQuery or underscore.js function?

Any help would be greatly appreciated.

A simple loop is probably more performant than any library call. Measure performance instead of being concerned. — Bergi
– Bergi, Commented Sep 12, 2014 at 9:41
In fact, jQuery's merge does exactly that. It just loops through the supplied arrays: merge:function(first,second){ for(;j<len;j++){ first[i++]=second[j]; } (And some more stuff) — Cerbrus
– Cerbrus, Commented Sep 12, 2014 at 9:47

Andy · Accepted Answer · 2014-09-12 09:53:29Z

10

There's no need to use a library for this.

For two arrays use concat:

var arr = obj.alpha.concat(obj.bravo);

For more than two arrays use a loop:

Either with concat again

var arr = [];
for (var k in obj) {
  arr = arr.concat(obj[k]);
}

Or using the push.apply method

var arr = [];
for (var k in obj) {
  arr.push.apply(arr, obj[k]);
}

DEMO

Make a function using this information so you don't need to repeat code:

function mergeObjectArrays(obj) {
  var arr = [];
  for (var k in obj) {
    arr.push.apply(arr, obj[k]);
  }
  return arr;
}

var arr = mergeObjectArrays(obj);

edited Sep 12, 2014 at 9:53

answered Sep 12, 2014 at 9:37

Andy

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Comments

paulitto · Accepted Answer · 2014-09-12 09:37:16Z

4

with jquery you can use merge

var newArray = $.merge(array1, array2);

with underscore you can use union

var newArray = _.union(array1, array2);

answered Sep 12, 2014 at 9:37

paulitto

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1 Comment

Seed Over a year ago

_.union does a merge; but it will only return unique values.

Matt · Accepted Answer · 2014-09-12 09:39:53Z

1

You can concat the arrays using pure javascript like this:

var obj =
{
    alpha: ["vatG4d6mcjKbpfuAm", "xkQrKEsfwuYPkDcdz", "GDg9chZnDGrbLXWGS"],
    bravo: ["53LEcQ5MoYXFyvktf"]
};
var obj.charlie = obj.alpha.concat(obj.bravo);

// obj.charlie = ["vatG4d6mcjKbpfuAm", "xkQrKEsfwuYPkDcdz", "GDg9chZnDGrbLXWGS", "53LEcQ5MoYXFyvktf"]

answered Sep 12, 2014 at 9:39

Matt

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