Is it possible to create a hidden property in javascript

Question

I want to create an object with a hidden property(a property that does not show up in a for (var x in obj loop). Is it possible to do this?

Answer 1

Nope, not possible. You can hide things by using closures though.

Answer 2

I think this is possible as long as the loop is not recursive (sort of inspired by Matti's answer above)

Consider this example.

var obj = {

  name: 'jim',
  age: '35',
  hidden: {status: 'cool'}

}

Your code above will produce the following output

jim
35
(object)

Answer 3

It isn't possible in ECMAScript 3 implementations (which covers all the current major browsers). However, in ECMAScript 5 which will be implemented in browsers soon, it is possible to set a property as non-enumerable:

var obj = {
   name: "Fred"
};

Object.defineProperty(obj, "age", {
    enumerable: false
});

obj.age = 75;

/* The following will only alert "name=>Fred" */
for (var i in obj) {
   window.alert(i + "=>" + obj[i]);
}

This does work in some current and imminent browsers: see http://kangax.github.com/es5-compat-table/ for details.