Return an object key only if value is true

Question

How do i return an object key name only if the value of it is true?

I'm using underscore and the only thing i see is how to return keys which is easy, i want to avoid redundant iterations as much as possible:

example:

Object {1001: true, 1002: false}  

I want an array with only 1001 in it...

Answer 1

Object.keys gets the keys from the object, then you can filter the keys based on the values

var obj = {1001: true, 1002: false};  var keys = Object.keys(obj);  var filtered = keys.filter(function(key) {     return obj[key] }); 

FIDDLE