AppFurnace: Utility function to load data from a .json file in the Files tab

LoadJSONFile.js

/**
 * Utility function to load JSON file a .json file in the Files tab.
 * 
 * Params:
 * @filename - the filename to use. Use the path to the file, e.g. "data.json" for a file in the root, or "data/content.json" for a file in a folder called content.
 * @callback - a function to call with the data when it's loaded. You'll need to provide a function with a parameter called 'data'/. e.g. function (data) { popup("I've got data!"); }
 * 
 * Example:
 * 
 * // Load a file called data.json....
 * loadJSONFromFiles("data.json", function(data) { 
 *        _.each(data, function(d) { // for each item..
 *          log( d.name " likes the color " + d.color); // .. log out the name and favorite color of each person.
 *       });
 * });
 * 
 * // data.json looks like this:
 * [
 *    {
 *       "name":"Ben",
 *       "color":"Blue"
 *   },
 *   {
 *       "name":"Tom",
 *       "color":"Orange"
 *   }
 * ]
 */
function loadJSONFromFiles(filename, callback) {
    $.ajax({
        url:"content/" + filename,
        success: function(data) {
            if (data) {
                if (_.isString(data)) {
                    try {
                        data = JSON.parse(data);
                    } catch (ex) {
                        popup(filename + " is not valid json");
                        callback( {} );
                        return;
                    }
                }
                callback( data );
            }
        },
        error: function(xhr) {
            popup("Failed to load " + filename + " server returned " + xhr.status);
            callback({});
        }
    });
}