Making a subset of an array of JavaScript objects based on one of their properties?

Question

I have a JavaScript array of objects with the same properties each, something like this:

box[0] = { name: 'somename', /* more properties... */ };
box[1] = { name: 'othername', /* more properties... */ };
box[2] = { name: 'onemorename', /* more properties... */ };
// more objects in the array...

I want to subset this array so that it only contains objects that match a "list" of names and copy the ones that don't to another array named cache maybe. I was thinking maybe I could compare this array of objects to another array which just contains a list of strings with the desired names to match against, checking each object's name property against this list to create a new array with the ones that matched. I don't know if this would work or if it is the best approach to achieve what I want, that is why I am asking for your help. Maybe checking each of 200-500 objects against a list with 100 names is not a very good thing to do, I don't know really.

Do you have any ideas on how I could do this? even better, can you point me to an example?

Thanks in advance.

Not a duplicate, but this questions comes very close to what you want: stackoverflow.com/questions/4893835/javascript-find-in-array — Felix Kling
– Felix Kling, Commented Feb 4, 2011 at 3:02

Anurag · Accepted Answer · 2011-02-04 03:11:19Z

0

Assuming the list of names you do want are stored in an array,

var wantedNames = [ "first name", "second name", .. ];

have two arrays - those matching a name and those that don't. Loop through each item in the box object, and if it contains a name from the list, then include it.

var objectsMatchingName = box.filter(function(item) {
    return wantedNames.indexOf(item.name) !== -1;
});

var cache = box.filter(function(item) {
    return objectsMatchingName.indexOf(item) === -1;
});

I wish there was a array difference operation of some kind, so you could do (in pseudocode):

var cache = box - objectsMatchingName

edited Feb 4, 2011 at 3:11

answered Feb 4, 2011 at 3:05

Anurag

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7 Comments

Raynos Over a year ago

forEach is not standard. & indexOf is not standard

Šime Vidas Over a year ago

@Raynos It's ECMAScript 5 I believe... es5.github.com/#x15.4.4.18 es5.github.com/#x15.4.4.14

VerizonW Over a year ago

Thanks, I am trying this right know with Underscore.js library so I can use forEach & indexOf, I'll let you know how it worked.

VerizonW Over a year ago

I think Underscore.js uses the native forEach & indexOf if available, if not it creates them so that will do I guess

Šime Vidas Over a year ago

@VerizonW It's implemented in every browser except IE8 and below kangax.github.com/es5-compat-table

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