underscore throttle using requestAnimationFrame

throttle-frame.js

// Returns a function, that, when invoked, will only be triggered once every
// browser animation frame - using tram's requestAnimationFrame polyfill.
// tram.js - https://github.com/bkwld/tram
_.throttle = function(func) {
  var wait, args, context;
  return function () {
    if (wait) return;
    wait = true;
    args = arguments;
    context = this;
    window.tram.frame(function () {
      wait = false;
      func.apply(context, args);
    });
  };
};

yairEO is right.