nextTick for browsers and Node.js

next_tick.js

// see => https://github.com/kriskowal/q/blob/v1/q.js#L83
// Use the fastest possible means to execute a task in a future turn
// of the event loop.
var nextTick =(function () {
    // linked list of tasks (single, with head node)
    var head = {task: void 0, next: null};
    var tail = head;
    var flushing = false;
    var requestTick = void 0;
    var isNodeJS = false;

    function flush() {
        /* jshint loopfunc: true */

        while (head.next) {
            head = head.next;
            var task = head.task;
            head.task = void 0;
            var domain = head.domain;

            if (domain) {
                head.domain = void 0;
                domain.enter();
            }

            try {
                task();

            } catch (e) {
                if (isNodeJS) {
                    // In node, uncaught exceptions are considered fatal errors.
                    // Re-throw them synchronously to interrupt flushing!

                    // Ensure continuation if the uncaught exception is suppressed
                    // listening "uncaughtException" events (as domains does).
                    // Continue in next event to avoid tick recursion.
                    if (domain) {
                        domain.exit();
                    }
                    setTimeout(flush, 0);
                    if (domain) {
                        domain.enter();
                    }

                    throw e;

                } else {
                    // In browsers, uncaught exceptions are not fatal.
                    // Re-throw them asynchronously to avoid slow-downs.
                    setTimeout(function() {
                       throw e;
                    }, 0);
                }
            }

            if (domain) {
                domain.exit();
            }
        }

        flushing = false;
    }

    nextTick = function (task) {
        tail = tail.next = {
            task: task,
            domain: isNodeJS && process.domain,
            next: null
        };

        if (!flushing) {
            flushing = true;
            requestTick();
        }
    };

    if (typeof process !== "undefined" && process.nextTick) {
        // Node.js before 0.9. Note that some fake-Node environments, like the
        // Mocha test runner, introduce a `process` global without a `nextTick`.
        isNodeJS = true;

        requestTick = function () {
            process.nextTick(flush);
        };

    } else if (typeof setImmediate === "function") {
        // In IE10, Node.js 0.9+, or https://github.com/NobleJS/setImmediate
        if (typeof window !== "undefined") {
            requestTick = setImmediate.bind(window, flush);
        } else {
            requestTick = function () {
                setImmediate(flush);
            };
        }

    } else if (typeof MessageChannel !== "undefined") {
        // modern browsers
        // http://www.nonblocking.io/2011/06/windownexttick.html
        var channel = new MessageChannel();
        // At least Safari Version 6.0.5 (8536.30.1) intermittently cannot create
        // working message ports the first time a page loads.
        channel.port1.onmessage = function () {
            requestTick = requestPortTick;
            channel.port1.onmessage = flush;
            flush();
        };
        var requestPortTick = function () {
            // Opera requires us to provide a message payload, regardless of
            // whether we use it.
            channel.port2.postMessage(0);
        };
        requestTick = function () {
            setTimeout(flush, 0);
            requestPortTick();
        };

    } else {
        // old browsers
        requestTick = function () {
            setTimeout(flush, 0);
        };
    }

    return nextTick;
})();