picturefill.js + jquery.lazyload

picturefill.js

/* 

This is a customised version of picturefill.js with the following modifications

1. Before setting the source on the img tag to the appropriate img file, check if the lazyload plugin is defined

2. If so, set the data-original attr of the img instead of the src attr. Also set width and height attrs from the picture span's data-width and data-height attrs. 

3. Append the img tag and tell lazyload about it

See demo - http://codepen.io/sheadawson/pen/fvFLc

*/

/*! Picturefill - Responsive Images that work today. (and mimic the proposed Picture element with span elements). Author: Scott Jehl, Filament Group, 2012 | License: MIT/GPLv2 */

(function( w ){

	// Enable strict mode
	"use strict";

	w.picturefill = function() {
		var ps = w.document.getElementsByTagName( "span" );

		// Loop the pictures
		for( var i = 0, il = ps.length; i < il; i++ ){
			if( ps[ i ].getAttribute( "data-picture" ) !== null ){

				var sources = ps[ i ].getElementsByTagName( "span" ),
					matches = [];

				// See if which sources match
				for( var j = 0, jl = sources.length; j < jl; j++ ){
					var media = sources[ j ].getAttribute( "data-media" );
					// if there's no media specified, OR w.matchMedia is supported 
					if( !media || ( w.matchMedia && w.matchMedia( media ).matches ) ){
						matches.push( sources[ j ] );
					}
				}

			// Find any existing img element in the picture element
			var picImg = ps[ i ].getElementsByTagName( "img" )[ 0 ];

			if( matches.length ){
				var matchedEl = matches.pop();
				if( !picImg || picImg.parentNode.nodeName === "NOSCRIPT" ){
					picImg = w.document.createElement( "img" );
					picImg.alt = ps[ i ].getAttribute( "data-alt" );
				}

				// should we lazyload?
				if(jQuery.fn.lazyload){
					// check if src has changed
					if(picImg.getAttribute('data-original') != matchedEl.getAttribute( "data-src" )){
						// set data-original attr for lazyload.js
						picImg.setAttribute('data-original', matchedEl.getAttribute( "data-src" ));
						// set width and height for lazyload.js placeholder
						picImg.setAttribute('width', matchedEl.getAttribute( "data-width" ));
						picImg.setAttribute('height', matchedEl.getAttribute( "data-height" ));
						// append the new image
						matchedEl.appendChild( picImg );
						// tell lazyload.js about our new/modified image
						$(picImg).lazyload();	
					}
				}else{
					// default picturefill functionality
					picImg.src =  matchedEl.getAttribute( "data-src" );
					matchedEl.appendChild( picImg );
				}
			}
			else if( picImg ){
				picImg.parentNode.removeChild( picImg );
			}
		}
		}
	};

	// Run on resize and domready (w.load as a fallback)
	if( w.addEventListener ){
		w.addEventListener( "resize", w.picturefill, false );
		w.addEventListener( "DOMContentLoaded", function(){
			w.picturefill();
			// Run once only
			w.removeEventListener( "load", w.picturefill, false );
		}, false );
		w.addEventListener( "load", w.picturefill, false );
	}
	else if( w.attachEvent ){
		w.attachEvent( "onload", w.picturefill );
	}

}( this ));