Question

Function.prototype.method = function (name, func) {
    this.prototype[name] = func;
    return this;
};

Stolen from Crockford’s Good Parts. When the code returns ‘this’, what does ‘this’ reference in this case?

I always ask myself this when I see ‘this’ inside a js code because I know that js is funky with the word this (i.e. ‘this’ actually references the global variable when it is used inside a nested function)

Answer 1

As you are extending Function.prototype, this will refer to a function instance.

Example:

function foo() {};

foo.method(); // `this` refers to foo

There are like four different ways of calling functions, which determine what this refers to. MDN has a good article about it.

In short:

• Simple function call: Global object (window in browsers)
• Object method: The object (i.e. obj.method(), this references obj) (that’s the case we have in your example)
• Using the new keyword: An empty object, inheriting from the functions prototype
• call / apply: Whatever you pass as first argument