The functions in JavaScript are objects, and they contain methods and properties. Some of the methods that you're already familiar with are apply() and call(), and some of the other properties are length and constructor. Another property of the function objects is prototype.
If you define a simple function, foo(), you can access its properties as you would do with any other object.
> function foo(a, b) {
return a * b;
}
> foo.length;
2
> foo.constructor;
function Function() { [native code] }
The prototype property is a property that is available to you as soon as you define the function. Its initial value is an "empty" object.
> typeof foo.prototype;
"object"
It's as if you added this property yourself as follows:
> foo.prototype = {};
You can augment this empty object with properties and methods. They won't have any effect on the
foo() function itself; they'll only be used if you call foo() as a constructor.