AMD module for loading a file asynchronously. It also stores the file in the browsers local storage for quicker access. I mostly use it for loading GLSL shader files

load-file.js

/*global define*/
/*
AMD module for loading files asynchronously. It also stores the contents of the files
in the browsers local storage for quicker access. I mostly use it for loading GLSL
shader files. Note: This has not been tested extensively, so use with caution.
MIT License
*/
define(
	function()
	{
		function FileLoader ()
		{
			var self = this;
			var files = { };
			var path_prefix = '';
			var path_suffix = '';
			var use_localstorage = ( window && localStorage && JSON );

			if ( use_localstorage )
			{
				files = JSON.parse( localStorage.getItem( 'file-loader' ) ) || { };
			}

			function load ( requested_files, loaded, complete )
			{
				var files_to_load = [ ];
				var files_arr = [ ];
				var files_obj = [ ];
				var files_loaded_count = 0;

				var i = 0;
				var len = 0;

				if ( typeof requested_files === 'string' )
				{
					requested_files = [ requested_files ];
				}
			
				for ( i = 0, len = requested_files.length; i < len; i++ )
				{
					var file_name = requested_files[i];

					if ( files_to_load.indexOf( file_name ) === -1 )
					{
						files_to_load.push( file_name );
					}
				}

				for ( i = 0, len = files_to_load.length; i < len; i++ )
				{
					loadFile( files_to_load[i] );
				}

				function loadFile ( file_name )
				{
					if ( typeof files[file_name] !== 'undefined' )
					{
						fileLoaded( file_name, files[file_name] );
					}

					else
					{
						var request = new XMLHttpRequest();
						
						request.onreadystatechange = function ()
						{
							if ( request.readyState === 4 )
							{
								fileLoaded( file_name, request.responseText );
							}
						};

						request.open( 'GET', path_prefix + file_name + path_suffix );
						request.send();
					}
				}

				function fileLoaded ( file_name, file_content )
				{
					// account for multiple occurencies in files_requested
					// but load them only once
					var indexes = getIndexes( file_name, requested_files );

					for ( var i = 0, len = indexes.length; i < len; i++ )
					{
						files_arr[indexes[i]] = file_content;
					}

					if ( typeof files[file_name] === 'undefined' )
					{
						files[file_name] = file_content;
						files_obj[file_name] = files[file_name];
						
						if ( use_localstorage )
						{
							localStorage.setItem( 'loader', JSON.stringify( files ) );
						}
					}
					
					files_loaded_count++;

					if ( typeof loaded === 'function' )
					{
						loaded( file_content );
					}

					if ( files_loaded_count === files_to_load.length )
					{
						if ( typeof callback === 'function' )
						{
							complete( files_obj, files_arr, requested_files );
						}
					}
				}
			}

			function getIndexes ( val, arr )
			{
				var result = [ ];

				for ( var i = 0, len = arr.length; i < len; i++ )
				{
					if ( arr[i] === val )
					{
						result.push( i );
					}
				}

				return result;
			}

			self.load = load;
		}

		return new FileLoader().load;
	}
);