throttler.js

var throttler = function(fn, maxExecutions) {
    var counter = 0,
        queue = [];

    return function() {
       var self = this,
           args = arguments,
           old_callback = args[args.length - 1];

       args[args.length - 1] = function() {
          counter -= 1;
          if(counter < maxExecutions && queue.length > 0) {
               counter += 1;
               fn.apply(self, queue.shift());
          }
          old_callback.apply(self, arguments);
       };

       if(counter < maxExecutions) {
          counter += 1;
          fn.apply(self, args);
       } else {
          queue.push(args);
       }
    };
}