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Wednesday, December 24, 2008

External selectors as engines and how to create your own library

With "Sizzle event", the challenge about libraries will move from the coolest/fastest selector engine into the coolest/fastest way to use it for library purpose.

Since Sizzle will be just one of them, thanks to our natural behavior ( read: re-create the wheel ) it is possible that there will be more selector engines around the net.

So, why we could not create our own library that does just what we need and nothing else, maintaining a decent size and performing like a jaguar :D ???

Here a truly basic example about how to create your own library, basing it over a generic selector engine or generic library (or just its engine, if you prefer one)

// our wonderful library constructor
function myQuery(){
// just in case we prefer another name for the constructor
// this code is "name proof"
var callee = arguments.callee;
return this instanceof callee ?
this :
callee.prototype.init.apply(new callee, arguments)

// add some native prototype to created array like instances
// a common pattern for DOM based libraries
myQuery.prototype = {

// add "not standard yet array prototypes", if necessary, or our own cool proottypes
myQuery.prototype.forEach = Array.prototype.forEach || function(Function, self){
for(var i = 0, length = this.length; i < length; i++)
(i in this) &&, this[i], i, this);

// define the init prototype to use the pre defined engine
myQuery.prototype.init = function(){
var self = this.engine.apply(null, arguments);
this.push.apply(this, self instanceof Array ? self :, 0));
return this;

// define the engine for this library
myQuery.prototype.engine = Sizzle; // or jQuery

onload = function(){

// enjoy your lib
myQuery(".foo .bar").forEach(function(HTMLElement){
HTMLElement.innerHTML = "Hello Lib!";



The main limit is the engine itself, or better, arguments that the engin could accept.
If we change engine and this accepts different arguments or same arguments in a different way, we need to change every call to our library but at least everything else will work without problems.
For this reason it is reasonble to choose a common engine arguments model, like Sizzle, for example, presuming other engine will accept the same list of options and will produce an array like result.
Am I suggesting to avoid famous/common library? Absolutely no, I simply think the selector engine is the most important thing for whatever DOM purpose library :-)

1 comment:

Marc said...

Hi Andrea,

I noticed some silence on your website, hope you're okay. Happy newyear!!! :)