does anyone know an npm module for this?

sync.js

(function() {
    var func, started;

    function sync(fn) {
        var running   = false,
            requested = [];

        return function me(callback) {
            if (running) {
                requested.push(callback);
                return;
            }

            running = true;

            fn(function() {
                callback.apply(this, arguments);

                running = false;
                if (requested.length) {
                    me(requested.shift());
                }
            });
        }
    }

    func = sync(function(callback) {
        setTimeout(callback, 1000);
    });

    started = Date.now();

    func(function() {
        console.log("after a while me #1", Date.now() - started);
    });

    func(function() {
        console.log("after a while me #2", Date.now() - started);
    });

    func(function() {
        console.log("after a while me #3", Date.now() - started);
    });
})();

Output:

after a while me #1 1019
after a while me #2 2038
after a while me #3 3039