Is there anyway to use a numeric type as an object key?

Question

It seems that when I use a numeric type as a key name in an object, it always gets converted to a string. Is there anyway to actually get it to store as a numeric? The normal typecasting does not seem to work.

Example:

var userId = 1;
console.log( typeof userId ); // number
myObject[userId] = 'a value';
console.dir(myObject);

Dir Output:

{
    '1': 'a value'
}

What I want is this:

{
    1: 'a value'
}

Advice?

Thanks

Answer 1

In JavaScript, numerical strings and numbers are interchangeable, so

myObject[1] == myObject['1']

If you really want number to be the key for an object, you might want an array (i.e. created with new Array() or []).

Answer 2

No, this is not possible. It will always be converted to a string. This is done in step 6 of the ECMAScript Property Accessor (§11.2.1) algorithm.

Answer 3

Appears to be by design in ECMA-262-5:

The Property Identifier type is used to associate a property name with a Property Descriptor. Values of the Property Identifier type are pairs of the form (name, descriptor), where name is a String and descriptor is a Property Descriptor value.

However, I don't see a definite specification for it in ECMA-262-3. Regardless, I wouldn't attempt to use non-strings as property names.