Question

I am seeing following line of code from source code of grunt npm module –

String.prototype.__defineGetter__(method, function() { return this; });

Just trying to anticipate what will be the value of ‘this’ inside the anonymous function above –

• It points back to ‘method’
• Global ‘window’ object if running in browser or something similar in grunt’s perspective
• Something else depending on the definition of defineGetter if call or apply are used inside the ‘defineGetter’ definition.

Thanks for the help !!

Answer 1

this will be the object on which the get operation occurs, which I think will always be the object on which you called __defineGetter__ (since I can’t immediately see a way to transfer that function elsewhere, but I wouldn’t guarantee you couldn’t; you’d have to do it on purpose, though).

It’s worth noting that __defineGetter__ is non-standard and obsolete. The current way to define a getter is to use Object.defineProperty or Object.defineProperties, like this:

Object.defineProperty(String.prototype, "foo", {
  get: function() {
    // Here, `this` is the string
    return this.toUpperCase();
  }
});

console.log("hi there".foo);

…which logs "HI THERE".

Live Example | Source