Why Object.keys is returns array of string instead of array of Numbers

Question

When I run following code

var obj = { 0: 'a', 1: 'b', 2: 'c' }; typeof Object.keys(obj)[0] //returns string 

In obj object i'm creating Number keys.

Any reason, why its string and not a number?

Answer 1

Keys are always of a String type. If you need numbers you will have to cast them manually:

var obj = { 0: 'a', 1: 'b', 2: 'c' };  var ids = Object.keys(obj).map(Number);    console.log(ids);