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+/*!
+ * Ext JS Library 3.2.1
+ * Copyright(c) 2006-2010 Ext JS, Inc.
+ * licensing@extjs.com
+ * http://www.extjs.com/license
+ */
+/**
+ * @class Ext.Loader
+ * @singleton
+ * Simple class to help load JavaScript files on demand
+ */
+Ext.Loader = Ext.apply({}, {
+ /**
+ * Loads a given set of .js files. Calls the callback function when all files have been loaded
+ * Set preserveOrder to true to ensure non-parallel loading of files if load order is important
+ * @param {Array} fileList Array of all files to load
+ * @param {Function} callback Callback to call after all files have been loaded
+ * @param {Object} scope The scope to call the callback in
+ * @param {Boolean} preserveOrder True to make files load in serial, one after the other (defaults to false)
+ */
+ load: function(fileList, callback, scope, preserveOrder) {
+ var scope = scope || this,
+ head = document.getElementsByTagName("head")[0],
+ fragment = document.createDocumentFragment(),
+ numFiles = fileList.length,
+ loadedFiles = 0,
+ me = this;
+
+ /**
+ * Loads a particular file from the fileList by index. This is used when preserving order
+ */
+ var loadFileIndex = function(index) {
+ head.appendChild(
+ me.buildScriptTag(fileList[index], onFileLoaded)
+ );
+ };
+
+ /**
+ * Callback function which is called after each file has been loaded. This calls the callback
+ * passed to load once the final file in the fileList has been loaded
+ */
+ var onFileLoaded = function() {
+ loadedFiles ++;
+
+ //if this was the last file, call the callback, otherwise load the next file
+ if (numFiles == loadedFiles && typeof callback == 'function') {
+ callback.call(scope);
+ } else {
+ if (preserveOrder === true) {
+ loadFileIndex(loadedFiles);
+ }
+ }
+ };
+
+ if (preserveOrder === true) {
+ loadFileIndex.call(this, 0);
+ } else {
+ //load each file (most browsers will do this in parallel)
+ Ext.each(fileList, function(file, index) {
+ fragment.appendChild(
+ this.buildScriptTag(file, onFileLoaded)
+ );
+ }, this);
+
+ head.appendChild(fragment);
+ }
+ },
+
+ /**
+ * @private
+ * Creates and returns a script tag, but does not place it into the document. If a callback function
+ * is passed, this is called when the script has been loaded
+ * @param {String} filename The name of the file to create a script tag for
+ * @param {Function} callback Optional callback, which is called when the script has been loaded
+ * @return {Element} The new script ta
+ */
+ buildScriptTag: function(filename, callback) {
+ var script = document.createElement('script');
+ script.type = "text/javascript";
+ script.src = filename;
+
+ //IE has a different way of handling <script> loads, so we need to check for it here
+ if (script.readyState) {
+ script.onreadystatechange = function() {
+ if (script.readyState == "loaded" || script.readyState == "complete") {
+ script.onreadystatechange = null;
+ callback();
+ }
+ };
+ } else {
+ script.onload = callback;
+ }
+
+ return script;
+ }
+});
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