util.js

/**
 * This function allows you to prefill "parts" of a functions
 * arguments.
 *
 * @param {Function} func The function to call
 * @param {mixed}         An argument
 * @param {mixed}         ...
 * 
 * @return {Function} Function with arguments that're prefilled
 *
 * Example:
 *
 * var waitForOneSecond = util.partial(setTimeout, null, 1000);
 *
 * waitForOneSecond(function() {
 *     // ... 
 * });
 */
partial: function() {
    var args = Array.prototype.slice.call(arguments);
    var func = args.shift();

    return function() {
        var passed = Array.prototype.slice.call(arguments);

        var funcArgs = args.map(function(arg) {
            if (arg === null) {
                arg = passed.shift();
            }

            return arg;
        });

        funcArgs = funcArgs.concat(passed);

        return func.apply(this, funcArgs);
    };
}