window.nextTick for the browser. ;-)

nextTick.js

/*
 * setTimeout(fn, 0) for realz, for modern browsers.
 * AKA nextTick from node.
 * Ripped from http://dbaron.org/log/20100309-faster-timeouts
 * Most browsers don't actually let you specify timeouts of 0, so the below
 * method is a better way of achieving this.
 * Philip Thrasher, 2012
 */
(function(){

    var timeouts = [],
        messageName = 'nextTickPlz',

        _nextTick = function(fn) {
            timeouts.push(fn);
            window.postMessage(messageName, "*");
        },

        _handleMessage(event) {
            if (event != null && event.source === window && event.data === messageName) {
                event.stopPropagation();
                if (timeouts.length > 0) {
                    var fn = timeouts.shift();
                    fn();
                }
            }
        };

        window.addEventListener("message", handleMessage, true);

        window.nextTick = _nextTick;
})();

This does not run:
you missed the function declaration for _handleMessage and handleMessage is not defined. Here's the fixed version:

(function(){

    var timeouts = [],
        messageName = 'nextTickPlz',

        _nextTick = function(fn) {
            timeouts.push(fn);
            window.postMessage(messageName, "*");
        },

        _handleMessage = function(event) {
            if (event != null && event.source === window && event.data === messageName) {
                event.stopPropagation();
                if (timeouts.length > 0) {
                    var fn = timeouts.shift();
                    fn();
                }
            }
        };

        window.addEventListener("message", _handleMessage, true);

        window.nextTick = _nextTick;
})();