Array.prototype.filter for objects.
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Deprecated - use MOUT

I built this planning to recreate the whole suite of Array extras and Underscore functional iterators for objects, sets, and maps, and then somebody pointed out that the bulk of this work has already been done. It's called MOUT, and it is completely modular. You can require the whole library, or only the function you need. Even better, the modularity works with AMD, Node, or Browserify, so you can use it just about everywhere you need it. This is where it's at, guys. Time to break our Underscore addiction.


Similar to Array.prototype.filter, except that it works on objects, and returns an object.


ofilter(object, callback[, thisObject])


object is the object you want to filter.

callback is a function that will be called for each key in object.

thisObject is an optional object to use for this inside callback.

var o = {
  a: {prop: 1},
  b: {prop: 'b'},
  c: {prop: 1}

filtered = ofilter(o, function (item) {
  return item.prop === 1;

ok(filtered.a && filtered.c,
  'should contain positive matches.'); // Pass

  'should not contain negative matches.'); // Pass

Crazy talk

This (along with several other common functional iterators) really needs to be part of the JavaScript specification. I can't recommend actually extending the Object prototype, but if you use ofilter() enough, maybe eventually, if we all believe hard enough, it will magically appear in a future version of the ECMAScript specification.

if (!Object.prototype.filter) {
  Object.prototype.filter = function (callback, thisObject) {
    return ofilter(this, callback, thisObject);

var obj = {a: 'a', b: 'b'};

var a = obj.filter(function (item) {
  return item === 'a';

t.same(a, {a: 'a'},
  'should work like Array.prototype.filter(). Come on, TC39!');