#Enhance.js

Enhance.js is a small JavaScript framework designed to help developers determine if a browser is qualified for enhancements, and load specific enhancements for that browser via a single, concatenated request (one for CSS and one for JavaScript).

• Copyright 2012 @scottjehl, @beep, @wilto, @maggiewachs, and Filament Group, Inc.
• Dual license: MIT or GPLv3

API

All of the Enhance api is available via window.ejs or just ejs. From ejs, you can access the following publicly:

Configuration Properties

• files: an object consisting of two empty child objects: js and css. These two objects are empty by default, and are intended for storing references to CSS** and JavaScript files that will potentially be loaded. You can reference them like so:

    // list of available JS files
    ejs.files.js = {
    	jQuery: "js/jquery.js",
    	touchNormalization: "touch.js",
    	uiLogic: "js/myapp.js"
    };
    
    // list of available CSS files
    ejs.files.css = {
    	accountPanel: "css/account.css"
    };
  

• basepath: an object consisting of two empty strings: js and css. These can be used to store optional base file paths to CSS and JS directories. When in use, you can exclude those paths from references to files in ejs.files.js and ejs.files.css. Example:

    // reference to base javascript filepath
    ejs.basepath.js = "assets/js/";
    
    // reference to base CSS filepath
    ejs.basepath.css = "assets/css/";
  

• concatSyntax: a predefined function that decorates a comma-delimited URL in whatever way necessary for a concatenator API. To configure, just redefine it as a function with a url argument, and return that url decorated any way your concatenator expects. By default, Enhance uses the url pattern suggested in the QuickConcat project. Example:

    // decorate URL for a custom concatenator API
    ejs.concatSyntax = function( url ){
    	return "/concat/" + url;
    };
  

Methods

• hasClass: check whether an element has a particular class or not. Returns a boolean result. Example:

    // check if HTML element has class of "ie8"
    ejs.hasClass( document.documentElement, "ie8" );
    --> true | false
  

• onDefine: run a callback function as soon as a JS property is defined, such as an HTML element like body that may not have loaded at execution time. Accepts 2 arguments: a string to be evaluated for definition, and a callback function to execute when that first string becomes defined. onDefine might be used to run a script when an element is ready for manipulation, such as checking if the body element has a particular class. Example:

    ejs.onDefine( "document.body", function(){
    	if( ejs.hasClass( document.body, "home" ) ){
    		// the body element has a class of "home"...
    	}
    });
  

  In a pinch, onDefine could also be used to delay code execution until another JS file has loaded and executed.

  note: onDefine uses asynchronous timing, so if you need to use it during your qualification and enhancement process, you'll need to ensure any logic that depends on the result of that callback executes afterwards, which can be acheived by wrapping it all in the onDefine callback.

• bodyReady: run a callback function when the body element is defined. Accepts one argument: a callback function to execute when the body element becomes defined. This is merely a shortcut to the onDefine example above. Example:

    ejs.bodyReady( function(){
    	if( ejs.hasClass( document.body, "home" ) ){
    		// the body element has a class of "home"...
    	}
    } );
  

  note: bodyReady uses asynchronous timing, so if you need to use it during your qualification and enhancement process, you'll need to ensure any logic that depends on the result of that callback executes afterwards, which can be acheived by wrapping it all in the bodyReady callback.

• addFile: add a CSS or JavaScript file to the queue for loading. This method accepts one argument, a string reference to a file. Example:

    ejs.addFile( "js/foo.js" );
    ejs.addFile( "css/foo.css" );
  

• enhance: load all queued CSS and JavaScript files via a single, concatenated request (per language). Example:

    ejs.enhance();
  

Additional Methods and Properties

Enhance has a few more methods and properties that you might use in more complicated scenarios.

• load: Load a single CSS** or JavaScript file. This method accepts one argument, a string reference to a file. The type of file is determined by file extension. Example:

    // Load a single css file
    ejs.load( "files/css/foo.css" );
    
    // Load a single JavaScript file
    ejs.load( "files/js/foo.js" );
  

• loadJS: Load a single JavaScript file. This method accepts one argument, a string reference to a file. Useful if JS filetype can not be guessed by filetype. Example:

    // Load a single JavaScript file
    ejs.loadJS( "files/js/foo.php" );
  

• loadCSS: Load a single CSS file. This method accepts one argument, a string reference to a file. Useful if CSS filetype can not be guessed by filetype. Example:

    // Load a single CSS file
    ejs.loadCSS( "files/css/foo.php" );
  

• jsToLoad: an array of JavaScript files currently in the queue for loading.

• cssToLoad: an array of CSS files currently in the queue for loading.

** Note: dynamically loaded CSS is not guaranteed to render before the page content begins visually rendering (and thus, can cause a FOUC). Don't depend on it for styles that need to be there during initial page load.

Typical workflow

While the Enhance core utility is very simple by itself; its real value is in the workflows it enables.

Check out the Southstreet project for an overview.