Why is my for loop not working on my Javascript properties?

Question

I created this object and it's properties:

var obj = {};

Object.defineProperty( obj, "value", {
  value: true,
  writable: false,
  enumerable: true,
  configurable: true
});

var name = "John";

Object.defineProperty( obj, "name", {
  get: function(){ return name; },
  set: function(value){ name = value; }
});

So then I call a for loop on them:

for ( var prop in obj ) {
  console.log( prop );
}

Which according to my tutorial, should produce the following results:

value
name

But instead it only displays value. Why is name not showing up?

Answer 1

The default value for enumerable in defineProperty is false; non-enumerable properties do not show up in for…in loops. (That's the whole point of the enumerable flag.) If you add enumerable:true into your second definition also, it will 'fix' it.

See some docs.

Answer 2

Because the name property is not defined as enumerable, set the name definition to

Object.defineProperty( obj, "name", {
  enumerable: true,
  get: function(){ return name; },
  set: function(value){ name = value; }
});

and it will show up.