How to Extend Prototypes with JavaScript

By  on  

One of the ideological sticking points of the first JavaScript framework was was extending prototypes vs. wrapping functions. Frameworks like MooTools and Prototype extended prototypes while jQuery and other smaller frameworks did not. Each had their benefits, but ultimately all these years later I still believe that the ability to extend native prototypes is a massive feature of JavaScript. Let's check out how easy it is to empower every instance of a primitive by extending prototypes!

Every JavaScript native, like Number, String, Array, Object, etc. has a prototype. Every method on a prototype is inherited by every instance of that object. For example, we can provide every `Array instance with a unique method by extending its prototype:

Array.prototype.unique = function() {
  return [...new Set(this)];
}

['1', '1', '2'].unique(); // ['1', '2']
new Array('1', '1', '2').unique(); // ['1', '2']

Note that if you can also ensure chaining capability by returning this:

['1', '1', '2'].unique().reverse(); // ['2', '1']

The biggest criticism of extending prototypes has always been name collision where the eventual specification implementation is different than the framework implementation. While I understand that argument, you can combat it with prefixing function names. Adding super powers to a native prototype so that every instance has it is so useful that I'd never tell someone not to extend a prototype. #MooToolsFTW.

Recent Features

  • By
    Create a CSS Flipping Animation

    CSS animations are a lot of fun; the beauty of them is that through many simple properties, you can create anything from an elegant fade in to a WTF-Pixar-would-be-proud effect. One CSS effect somewhere in between is the CSS flip effect, whereby there's...

  • By
    Chris Coyier’s Favorite CodePen Demos

    David asked me if I'd be up for a guest post picking out some of my favorite Pens from CodePen. A daunting task! There are so many! I managed to pick a few though that have blown me away over the past few months. If you...

Incredible Demos

  • By
    MooTools 1.2 Tooltips: Customize Your Tips

    I've never met a person that is "ehhhh" about XHTML/javascript tooltips; people seem to love them or hate them. I'm on the love side of things. Tooltips give you a bit more information about something than just the element itself (usually...

  • By
    Highlight Table Rows, Columns, and Cells Using MooTools 1.2.3

    Row highlighting and individual cell highlighting in tables is pretty simple in every browser that supports :hover on all elements (basically everything except IE6). Column highlighting is a bit more difficult. Luckily MooTools 1.2.3 makes the process easy. The XHTML A normal table. The cells...

Discussion

    Wrap your code in <pre class="{language}"></pre> tags, link to a GitHub gist, JSFiddle fiddle, or CodePen pen to embed!