Use of Async IF construct

use_async_if.js

/* function to detect if a box of given color is visible on screen or not */
is_box_visible = function(color) {
    var selector;
    selector = "." + color + "box:visible";
    return $(selector).length > 0;
};

$.when(async_if(is_box_visible, 'green') /* green box is visible */, 
       async_if(is_box_visible, 'red') /* red box is visible */
      ).then(
        function() {
               /* when both the red and green box appeared, inject a blue box */
               inject_box('blue');
        }
);

/* a timeout sample usecase, detect a redbox within 10seconds of start */
async_if(is_box_visible, 'red', 10000).then(
       function(color) { 
              alert('red box detected'); 
       }, 
      function(status) {
          alert("couldn't detect redbox 10 seconds....");
      });