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

I suppose you could add a new method to the prototype:

if (!('keepOnlyTheseProps' in Object.prototype)) {
  Object.prototype.keepOnlyTheseProps = function (arr) {
    var keys = Object.keys(this);
    for (var i = 0, l = keys.length; i < l; i++) {
      if (arr.indexOf(keys[i]) < 0) delete this[keys[i]];
    }
  }
}

myObj.keepOnlyTheseProps(['p1', 'p2', 'p100']);

Fiddle.