Async chained callback pattern.

chain.js

(function(){

/**
 * Function.asyncChain( fn, [...] ) -> Function
 * 
 * Takes any number of callback functions and returns a scheduler function 
 * which manages the chain. Each supplied callback to should take one 
 * argument, the scheduler, to execute with no arguments when it completes.
 * 
 * Example:
 * 
 * // Waits 100ms before doing stuff
 * function doA(fn){
 *      setTimeout(function(){
 *          console.log("A doing stuff!");
 *          fn();
 *      }, 100);
 * }
 * 
 * // Makes an ajax request using jQuery and does stuff in the response
 * function doB(fn){
 *      // Note this will not continue the chain on error, as the handler does not fire
 *      $.getJSON('foo.json', { bar:1 }, function(data){
 *          console.log("B see reply:", data);
 *          fn();
 *      });
 * }
 * 
 * var scheduler = Function.asyncChain(doA, doB);
 * 
 * // Kick off chain
 * scheduler();
 * 
 * 
 * Protip: use closures to collect other arguments or context. 
 * 
 * Advanced: Note that the scheduler will pass along the execution context 
 * (this) it is invoked with allowing you to override the return context if 
 * you wish.
 * 
 */
function asyncChain(fn){
    var callbacks = Array.prototype.slice.call(arguments, 0);
    scheduler.add = function(){
        var args = Array.prototype.slice.call(arguments, 0);
        while (args.length) callbacks.push(args.shift());
    };
    return scheduler;
    
    function scheduler(){
        if ( !callbacks.length )
            return;
        else 
            return callbacks.shift().call( this, arguments.callee );
    }
}
Function.asyncChain = asyncChain;

})();