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 Cube

    CSS cubes really showcase what CSS has become over the years, evolving from simple color and dimension directives to a language capable of creating deep, creative visuals.  Add animation and you've got something really neat.  Unfortunately each CSS cube tutorial I've read is a bit...

  • By
    Responsive Images: The Ultimate Guide

    Chances are that any Web designers using our Ghostlab browser testing app, which allows seamless testing across all devices simultaneously, will have worked with responsive design in some shape or form. And as today's websites and devices become ever more varied, a plethora of responsive images...

Incredible Demos

  • By
    Making the Firefox Logo from HTML

    When each new t-shirt means staving off laundry for yet another day, swag quickly becomes the most coveted perk at any tech company. Mozilla WebDev had pretty much everything going for it: brilliant people, interesting problems, awesome office. Everything except a t-shirt. That had to change. The basic...

  • By
    CSS Fixed Positioning

    When you want to keep an element in the same spot in the viewport no matter where on the page the user is, CSS's fixed-positioning functionality is what you need. The CSS Above we set our element 2% from both the top and right hand side of the...

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!