$loader (pronounced "money-loader") is a simple script for using either the embedded version of jQuery or loading your own copy but saving a reference in your own scope. The primary use-case for this is in development of code that will be embedded into ot

$loader.js

// Load jQuery.
var $loader = function(callback) {
	this.callback = callback;
	this.check$();
}
$loader.prototype = {
	// Check to see if we have our own copy of jQuery.
	check$: function(version) {
		// Load event version.
		// TODO: Limit to our earliest supported version of jQuery.

		if (window.jQuery) {
			// jQuery is already in existence, use their copy.
			this.have$(true);
		} else {
			// First call and jQuery doesn't exist, load us a copy.
			this.load$(version);
		}

		// Timeout version.
		/*
		if (first && window.jQuery) {
			// jQuery is already in existence, use their copy.
			// TODO: Limit to our earliest supported version of jQuery.
			this.have$(first);
		} else if (first) {
			// First call and jQuery doesn't exist, load us a copy.
			this.load$();
		} else if (window.jQuery) {
			// We've loaded our own jQuery, got here via a setTimeout call.
			this.have$();
		} else {
			setTimeout(this.arguments.callee, 200);
		}
		*/
	},

	// Get our own copy of jQuery.
	load$: function(version) {
		var self = this;
		version = version || '1.5.2'
		
		// Build our script tag.
		var s = document.createElement('script');
		s.type = 'text/javascript';
		s.async = true;
		s.src = ('https:' == document.location.protocol ? 'https://' : 'http://') + 'ajax.googleapis.com/ajax/libs/jquery/'+version+'/jquery.min.js';
		
		// Load event version.
		s.onload = function() {
			self.have$();
		}
		s.onreadystatechange = function() {
			if (this.readyState == 'complete' || this.readyState == 'loaded') {
				self.have$();
			}
		}

		var o = document.getElementsByTagName('script')[0];
		o.parentNode.insertBefore(s, o);
	},

	// Save a reference for ourselves!
	have$: function(first) {
		// Pass the reference to the callback.
		var reference;

		if (first) {
			// We're using their copy.
			reference = window.jQuery;
		} else {
			// We're using our copy, get jQuery back out of their global scope.
			reference = window.jQuery.noConflict(true);					
		}

		this.callback(reference);
	}
};

// Usage
new $loader(function(reference) {
	// Intentionally leaking $, it should be defined in the correct (private) scope.
	$ = reference;
});

readme.md

$loader (pronounced "money-loader") is a simple script for using either the embedded version of jQuery or loading your own copy but saving a reference in your own scope. The primary use-case for this is in development of code that will be embedded into others' sites.

If you have multiple chained dependencies (other than just jQuery) I instead recommend embedding LABjs and modifying it to leak $LAB from its own scope into yours.