Javascript - Object, for loop starting at 2

Question

I have objects looking like this.

foo = {
    0 : {
        'bar' : 'baz',
        'qux' : 'quux',
        'this' : { 'hello' : 'yes' } // this is the object I want to extract
    }
    1 : {
        'bar' : 'baz',
        'qux' : 'quux',
        'this' : { 'hello' : 'yes' } // extract
    }
    2 : {
        'bar' : 'baz',
        'qux' : 'quux',
        'this' : { 'hello' : 'yes' }, // extract
        'that' : { 'hello' : 'no' } // extract
    }
}

with a for loop like this I get to loop through every object:

for(var i in foo){
  ...
}

The problem is that I only want to pull the data from the third and greater child object than ('this') from each object.

Objects are unordered. There isn't really a concept of a "first" or "second" key-value pair. Are you just trying to get all keys that happen to have values that are objects? — Blender
– Blender, Commented Apr 4, 2013 at 9:13
@Philip: There is no order. That's just the way they're being displayed. — Blender
– Blender, Commented Apr 4, 2013 at 9:14

jAndy · Accepted Answer · 2013-04-04 09:14:46Z

2

There is no specified order for object keys in ECMAscript. You really should use an Javascript Array if you have indexed key names nonetheless.

If you need to have a plain Object, you might want to use Object.keys() alongside Array.prototype.forEach and .sort(), like

Object.keys( foo ).sort().forEach(function( i ) {
});

If you can't rely on ES5, you have no choice but to do the work manually.

var keys = [ ];

for(var key in foo) {
    if( foo.hasOwnProperty( key ) ) {
        keys.push( key );
    }
}

keys.sort();

for(var i = 0, len = keys.length; i < len; i++) {
}

However, you really should just use an Array in the first place, so you can skip the dirty work.

answered Apr 4, 2013 at 9:14

jAndy

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3 Comments

Philip Over a year ago

The problem is that I can't use Object.keys with IE.

Philip Over a year ago

Thanks for the solution, I think that I will make an array of it instead.! =)

Moritz Roessler Over a year ago

Wouldn't var cnt = 1,cur;while (cur = foo[++cnt]) {...} work too, though it still doesn't make much sense using an object

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