gistfile1.js

function(func, hasher) {
    var cache = {},
        queue = {};
    hasher = hasher || JSON.stringify;
    return function() {
        var args = Array.prototype.splice.call(arguments, 0);
        var callback = args.pop();
        var hash = hasher(args);
        if (hash in cache) {
            callback.apply(this, cache[hash]);
        } else if (hash in queue) {
            queue[hash].push(callback);
        } else {
            queue[hash] = [callback];
            args.push(function() {
                cache[hash] = Array.prototype.splice.call(arguments, 0);
                var q = queue[hash];
                delete queue[hash];
                q.forEach(function(qcallback) {
                    qcallback.apply(null, cache[hash]);
                });
            });
            func.apply(this, args);
        }
    };
};