Keeping only certain properties in a JavaScript object

Question

I have an object. I would like to modify the object (not clone it) by removing all properties except for certain specific properties. For instance, if I started with this o

Answer 1

var myObj = {a: 1, b: 2, c:3};

function keepProps(obj, keep) {
    for (var prop in obj) {
        if (keep.indexOf( prop ) == -1) {
            delete obj[prop];
        }             
    }
}

keepProps(myObj, ['a', 'b']);
console.log(myObj);

http://jsfiddle.net/mendesjuan/d8Sp3/2/