/*jslint browser: true, eqeqeq: true, bitwise: true, newcap: true, immed: true, regexp: false */ /** LazyLoad makes it easy and painless to lazily load one or more external JavaScript or CSS files on demand either during or after the rendering of a web page. Supported browsers include Firefox 2+, IE6+, Safari 3+ (including Mobile Safari), Google Chrome, and Opera 9+. Other browsers may or may not work and are not officially supported. Visit https://github.com/rgrove/lazyload/ for more info. Copyright (c) 2011 Ryan Grove All rights reserved. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. @module lazyload @class LazyLoad @static */ LazyLoad = (function (doc) { // -- Private Variables ------------------------------------------------------ // User agent and feature test information. var env, // Reference to the element (populated lazily). head, // Requests currently in progress, if any. pending = {}, // Number of times we've polled to check whether a pending stylesheet has // finished loading. If this gets too high, we're probably stalled. pollCount = 0, // Queued requests. queue = {css: [], js: []}, // Reference to the browser's list of stylesheets. styleSheets = doc.styleSheets; // -- Private Methods -------------------------------------------------------- /** Creates and returns an HTML element with the specified name and attributes. @method createNode @param {String} name element name @param {Object} attrs name/value mapping of element attributes @return {HTMLElement} @private */ function createNode(name, attrs) { var node = doc.createElement(name), attr; for (attr in attrs) { if (attrs.hasOwnProperty(attr)) { node.setAttribute(attr, attrs[attr]); } } return node; } /** Called when the current pending resource of the specified type has finished loading. Executes the associated callback (if any) and loads the next resource in the queue. @method finish @param {String} type resource type ('css' or 'js') @private */ function finish(type) { var p = pending[type], callback, urls; if (p) { callback = p.callback; urls = p.urls; urls.shift(); pollCount = 0; // If this is the last of the pending URLs, execute the callback and // start the next request in the queue (if any). if (!urls.length) { callback && callback.call(p.context, p.obj); pending[type] = null; queue[type].length && load(type); } } } /** Populates the env variable with user agent and feature test information. @method getEnv @private */ function getEnv() { var ua = navigator.userAgent; env = { // True if this browser supports disabling async mode on dynamically // created script nodes. See // http://wiki.whatwg.org/wiki/Dynamic_Script_Execution_Order async: doc.createElement('script').async === true }; (env.webkit = /AppleWebKit\//.test(ua)) || (env.ie = /MSIE|Trident/.test(ua)) || (env.opera = /Opera/.test(ua)) || (env.gecko = /Gecko\//.test(ua)) || (env.unknown = true); } /** Loads the specified resources, or the next resource of the specified type in the queue if no resources are specified. If a resource of the specified type is already being loaded, the new request will be queued until the first request has been finished. When an array of resource URLs is specified, those URLs will be loaded in parallel if it is possible to do so while preserving execution order. All browsers support parallel loading of CSS, but only Firefox and Opera support parallel loading of scripts. In other browsers, scripts will be queued and loaded one at a time to ensure correct execution order. @method load @param {String} type resource type ('css' or 'js') @param {String|Array} urls (optional) URL or array of URLs to load @param {Function} callback (optional) callback function to execute when the resource is loaded @param {Object} obj (optional) object to pass to the callback function @param {Object} context (optional) if provided, the callback function will be executed in this object's context @private */ function load(type, urls, callback, obj, context) { var _finish = function () { finish(type); }, isCSS = type === 'css', nodes = [], i, len, node, p, pendingUrls, url; env || getEnv(); if (urls) { // If urls is a string, wrap it in an array. Otherwise assume it's an // array and create a copy of it so modifications won't be made to the // original. urls = typeof urls === 'string' ? [urls] : urls.concat(); // Create a request object for each URL. If multiple URLs are specified, // the callback will only be executed after all URLs have been loaded. // // Sadly, Firefox and Opera are the only browsers capable of loading // scripts in parallel while preserving execution order. In all other // browsers, scripts must be loaded sequentially. // // All browsers respect CSS specificity based on the order of the link // elements in the DOM, regardless of the order in which the stylesheets // are actually downloaded. if (isCSS || env.async || env.gecko || env.opera) { // Load in parallel. queue[type].push({ urls : urls, callback: callback, obj : obj, context : context }); } else { // Load sequentially. for (i = 0, len = urls.length; i < len; ++i) { queue[type].push({ urls : [urls[i]], callback: i === len - 1 ? callback : null, // callback is only added to the last URL obj : obj, context : context }); } } } // If a previous load request of this type is currently in progress, we'll // wait our turn. Otherwise, grab the next item in the queue. if (pending[type] || !(p = pending[type] = queue[type].shift())) { return; } head || (head = doc.head || doc.getElementsByTagName('head')[0]); pendingUrls = p.urls.concat(); for (i = 0, len = pendingUrls.length; i < len; ++i) { url = pendingUrls[i]; if (isCSS) { node = env.gecko ? createNode('style') : createNode('link', { href: url, rel : 'stylesheet' }); } else { node = createNode('script', {src: url}); node.async = false; } node.className = 'lazyload'; node.setAttribute('charset', 'utf-8'); if (env.ie && !isCSS && 'onreadystatechange' in node && !('draggable' in node)) { node.onreadystatechange = function () { if (/loaded|complete/.test(node.readyState)) { node.onreadystatechange = null; _finish(); } }; } else if (isCSS && (env.gecko || env.webkit)) { // Gecko and WebKit don't support the onload event on link nodes. if (env.webkit) { // In WebKit, we can poll for changes to document.styleSheets to // figure out when stylesheets have loaded. p.urls[i] = node.href; // resolve relative URLs (or polling won't work) pollWebKit(); } else { // In Gecko, we can import the requested URL into a