Python-like string interpolation in Javascript

/**
 * Provides python-like string interpolation.
 * It supports value interpolation either by keys of a dictionary or
 * by index of an array.
 *
 * Examples::
 *
 *      interpolate("Hello %s.", ["World"]) == "Hello World."
 *      interpolate("Hello %(name)s.", {name: "World"}) == "Hello World."
 *      interpolate("Hello %%.", {name: "World"}) == "Hello %."
 *
 * This version doesn't do any type checks and doesn't provide
 * formating support.
 */
function interpolate(s, args) {
    var i = 0;
    return s.replace(/%(?:\(([^)]+)\))?([%diouxXeEfFgGcrs])/g, function (match, v, t) {
        if (t == "%") return "%";
        return args[v || i++];
    });
}