Extend Native Prototypes in Node.js

By  on  

As someone who was on the legendary MooTools JavaScript team, I have some affection for extending the prototypes of native objects.  Of course the practice of extending prototypes is taboo these days as browser vendors are iterating and implementing new specs more quickly than the IE6 era, but extending natives in Node.js could be considered safer as, in theory, we have more control over the environment (Node.js version).

Extending a native within Node.js is fairly simple:

// Inside a file module called "String.prototype.startsWith.js"
// Naming convention important for maintenance and clearness of intent

// This is a very, very simple shim not made for production use
// It's simply to illustrate the prototype extension
// More logic should be added for edge cases 
if(!String.prototype.startsWith) {
  String.prototype.startsWith = function(term) {
    return this.substr(0, term.length) === term;
  };
}

// ----------

// Inside any other module that wants to use the extension
require('String.prototype.startsWith');

// Usage
if(myString.startsWith('Moo')) {
  // ...
}

As long as you require the the module that contains the extension code, the native will have its desired additional method.  Of course this doesn't just apply to natives, you can extend other Objects in this same fashion.  If you scour npm you can find loads of prototype extensions, one being String.prototype.startsWith, which also work in client side code.

I presume I'll receive some haterade for suggesting this practice being more OK with Node.js so have at me!

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
    How to Create a RetroPie on Raspberry Pi – Graphical Guide

    Today we get to play amazing games on our super powered game consoles, PCs, VR headsets, and even mobile devices.  While I enjoy playing new games these days, I do long for the retro gaming systems I had when I was a kid: the original Nintendo...

Incredible Demos

  • By
    LightFace:  Facebook Lightbox for MooTools

    One of the web components I've always loved has been Facebook's modal dialog.  This "lightbox" isn't like others:  no dark overlay, no obnoxious animating to size, and it doesn't try to do "too much."  With Facebook's dialog in mind, I've created LightFace:  a Facebook lightbox...

  • By
    Custom Scrollbars in WebKit

    Before each of the browser vendors we like was providing unique CSS controls, Internet Explorer was setting the tone.  One such example is IE's early implementation of CSS filters. Internet Explorer was also the first browser that allowed developers to, for better or worse, customize...

Discussion

  1. Ricardo

    In fact, I don’t see much problem extending String/Array/… objects in client side code. When the browser supports it, then the polyfill will not be used.
    About extending host objects (DOMElement…), the main problem was IE6-7. Recent browsers have no problem with it, even if that does not belong to the specification

  2. MaxArt

    Never had any problem extending native prototypes, but there are a few caveats:

    – you either polyfill standard methods (like startsWith above) or use names that won’t probably be used by future standard developments, such as vectorDotProduct;
    – don’t abuse this technique: changing prototypes is *slow* and also user-defined methods in the prototype chain are;
    – unless you make a module out of your extensions, remember that your code will be less reusable.

  3. “extending natives in Node.js” should “be considered safer as, in theory,” upgrading Node.js breaks everything :P

    Kidding, my v0.11 to v4 upgrade was actually pretty smooth.

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