Javascript - Store variable as object and function

Question

I've seen instances of a variable being both an object and a string. Example:

alert(x + ""); // Hello
alert(x()); // World

This kind of thing is what jQuery does with the $ variable.

How might you get this effect?

You don't use jQuery's $ like in your first example. jQuery's $ is simply a function which also has properties (which might be functions themselves). The toString mentioned in the answers is rarely useful to override. — Ingo Bürk
– Ingo Bürk, Commented Aug 14, 2014 at 22:57
Are you sure that's what jQuery does? Last time I looked, many (most?) of its methods are overloaded and do stuff depending on whether they are passed a Function, Object, string, whatever, rather than overwriting or replacing built–in methods. — RobG
– RobG, Commented Aug 14, 2014 at 22:57
Also, jQuery does not override toString (despite it not being useful anyway). You can see that by simply opening the console on SO and typing $.toString() or make sure via $.toString === Function.prototype.toString, which comes out true. — Ingo Bürk
– Ingo Bürk, Commented Aug 14, 2014 at 23:02
jQuery allows you to do $.xyz(); or $(".abc").xyz();. That's what I was talking about. — Potassium Ion
– Potassium Ion, Commented Aug 14, 2014 at 23:04
@tupperkion any function can have properties, because functions are objects. — Pointy
– Pointy, Commented Aug 14, 2014 at 23:07

Oriol · Accepted Answer · 2014-08-14 22:59:18Z

5

No, a variable can't be both an object and a (primitive) string.

However, if you attempt to convert an object to a string (e.g. using obj + ''), the string returned by its toString method is used instead.

function x() {
    return "World";
}
x.toString = function() {
    return "Hello";
};

answered Aug 14, 2014 at 22:54

Oriol

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1 Comment

And vice versa, primitives are converted to Objects for the sake of evaluation of expressions: 'blah'.split(). ;-)