responsiveimgs.js

/*!
 * Responsive Images: Mobile-First images that scale responsively and responsibly
 * Copyright 2011, Scott Jehl, Filament Group, Inc
 * Dual licensed under the MIT or GPL Version 2 licenses.
*/
(function( win ){
	//defaults / mixins
	var	rwdi			= win.rwd_images || {},
		widthBreakPoint	= rwdi.widthBreakPoint || 480,
		htmlClass		= "rwd-imgs-lrg",
		wideload		= win.screen.availWidth > widthBreakPoint,
		filePath		= location.href,
		dirPath			= filePath.substring( 0, filePath.lastIndexOf( "/" ) ) + "/",
		doc				= win.document,
		head			= doc.getElementsByTagName( "head" )[0],
		
		//record width cookie for subsequent loads
		date			= new Date();
		date.setTime(date.getTime()+(5/*5 sec*/*1000));
		doc.cookie = "rwd-resolution=" + screen.width + ";expires=" + date.toGMTString() +"; path=/";

		//if wideload is false quit now
		if( !wideload ){
			return;
		}
		
		//add HTML class
		doc.documentElement.className += " " + htmlClass;
		
		//base tag support test (returns base tag for use if support test passes) creds: jQuery Mobile, hasJS
		var base		= (function(){
			var backup,
				baseAdded = false,
				a = doc.createElement("a"),
				supported = false,
				base = head.getElementsByTagName( "base" )[0] || (function(){
	                baseAdded = true;
	                return head.insertBefore( doc.createElement("base"), head.firstChild );
	            })();
	         
	        backup = !baseAdded && base.href;   
	        
	        //test base support before using
            base.href = location.protocol + "//" + "x/";
            a.href = "y";
            
            //if dynamic base tag is unsupported (Firefox)
            if( a.href.indexOf( "x/y" ) < 0 ){
            	if( backup ){
            		base.href = backup;
            	}
            	else{
            		head.removeChild(base);
            	}
            	base = null;
            }
            else{
            	base.href = dirPath +  "rwd-router/";
            }
            //return 
			return base;
	    })(),
	    
	    //find and replace img elements
		findrepsrc		= function(){
			for( var i = 0, imgs = doc.getElementsByTagName( "img" ), il = imgs.length; i < il; i++){
				var img		= imgs[i],
					src		= img.getAttribute( "src" ),
					full	= src.match( /(\?|&)full=(.*)&?/ ) && RegExp.$2;
					
				if( full ){
					img.src = full;
				}
			}
		},
		
		//flag for whether loop has run already
	    complete		= false,
	    
	    //remove base if present, find/rep image srcs if wide enough (maybe make this happen at domready?)
	    readyCallback	= function(){
	    	if( complete ){ return; }
	    	complete = true;

	    	if( !base ) {
				findrepsrc();
			}
			else{
				head.removeChild(base);
			}
	    };
	
	//DOM-ready or onload handler
	//W3C event model
	if ( doc.addEventListener ) {
		win.addEventListener( "load", readyCallback, false );
	}
	// If IE event model is used
	else if ( doc.attachEvent ) {
		win.attachEvent( "onload", readyCallback );
	}
})(this);