Named parameters application of a function

gistfile1.js

/**
 * Applies a set of named arguments to `fn`.
 *
 * Example: var f = function(x, y, z) { return x * (y - z); };
 *          namedApply(f, {x: 1, y: 2, z: 3});
 * 
 * @param fn {Function} A function to invoke.
 * @param args {Object} A collection of named arguments.
 */
function namedApply(fn, args) {
    // Validation
    if (typeof(fn) != "function")
        throw new TypeError("namedApply(fn, args): `fn` must be a function");
    
    // Make sure `args` is not null or undefined
    args = args || {};

    // Converts `args` object into array with arguments to be passed into `fn`
    args = fn.toString()
             // Gets a list of parameter names from `fn` body
             // TODO: make it work with embeded comments: function (a, b /* optional */) { }
             //       and also optimization is needed
             .match(/function[^(]*\((.*?)\)/)[1].split(/\s*,\s*/)
             // Maps parameter names to values from `args`
             .map(function(name){ return args[name] });
    return fn.apply(this, args);
}

Note! It's just a basic implementation, not all the possible scenarios are covered here and performance hasn't been taken into consideration.