An example for how you might possibly use jQuery Deferred Object.

jquery-deferred-example.js

function doHeavyWork() {
  var deferred = $.Deferred(),
      meaningOfLife = new Array();

  setTimeout(function() {
    for (var i = 0; i < 65536; i++) {
      meaningOfLife[i] = new Array();
      for (var j = 0; j < 65536; j++) {
        meaningOfLife[i][j] = new Array();
        for (var k = 0; k < 65536; k++) {
          meaningOfLife[i][j][k] = 42;
        }
      }
    }
    deferred.resolve("The meaning of Life is 42.");
  }, 100);

  return deferred.promise();
}

var heavyWork = doHeavyWork();

heavyWork.done(function(msg) {
  window.alert(msg);
});