Simple async.js-like dependent task processing

dep.js

function process_reqs (reqs) {
    var dependents = {}; // name -> [dependents]
    var completed = {};
    var pending_cnts = {};
    var hasOwn = Object.prototype.hasOwnProperty;
    var leaf_tasks = [];

    for (var key in reqs) {
        if (!hasOwn.call(reqs, key)) continue;

        var deplist = reqs[key].deps;
        pending_cnts[key] = deplist.length;
        if (deplist.length === 0) {
            leaf_tasks[leaf_tasks.length] = key;
        } else {
            for (var i = 0; i < deplist.length; i++) {
                var dep = deplist[i], ds;
                if (hasOwn.call(dependents, dep)) {
                    ds = dependents[dep];
                } else {
                    ds = dependents[dep] = [];
                }
                ds[ds.length] = key;
            }
        }
    }

    schedule (leaf_tasks);

    function createCompletionCallback (task) {
        return function () {
            var targets = dependents[task];
            var sched_tasks = [];

            if (!targets) return;
            delete dependents[task];
            completed[task] = [].slice.call(arguments);

            for (var i = 0; i !== targets.length; i++) {
                var key = targets[i];
                if (!--pending_cnts[key]) { // completed
                    sched_tasks[sched_tasks.length] = key;
                }
            }

            schedule (sched_tasks);
        }
    }

    function schedule (sched_tasks) {
        sched_tasks.sort(function (a, b) {
            return reqs[b].priority - reqs[a].priority;
        });

        while (sched_tasks.length) {
            var sched_key = sched_tasks.pop();
            //console.log("processing " + sched_key + "...");
            var cc = createCompletionCallback(sched_key);
            try {
                reqs[sched_key].process(completed, cc);
            } catch (e) {
                console.log("an error occured while processing " + sched_key + ": " + e.stack);
                cc(e, null);
            }
            cc = null;
        }
    }
}