Question

Is there a way to iterate over properties in an object without using a for in loop?

According to Nicholas C. Zakas, it takes 8x longer for a for in loop to iterate over an object than a for loop, but i cant find a way to iterate over the properties of an object without changing their names to something like 1, 2, 3 etc. witch isn’t ideal.

Speed is the main concern for me.

Answer 1

You can have another array that holds your keys. Something like this:

var obj = {
    'key': 'value',
    'some': 'other value'
},
    arr = [ 'key', 'some' ];

for ( var i = 0, l = arr.length; i < l; i++ ) {
    console.log( obj[ arr[ i ] ] );
}

However, that’s ugly. Performance in this kind of case will never be your bottleneck, you should rather prefer readability. The code up there can be done this way:

Object.keys( obj ).forEach( function( key ) {
    console.log( obj[ key ] );
} );

Which is just way cleaner and more readable. (for..in could also be used, it was just for the sake of the example)