Construct a URL path, replacing ":placeholder" with values

url.js

define([
    'src/urls'
], function(
    urls
) {
    'use strict';

    var slice = Array.prototype.slice;

    return function url(name) {
        if (!(name in urls)) {
            throw name + " is not a valid url";
        }

        var route = '/' + urls[name][0],
            params = slice.call(arguments, 1),
            lastArg = params[params.length - 1],
            queryString = "";

        if (typeof lastArg === "object") {
            queryString = "?" + $.param(lastArg);
            params = params.slice(0, params.length - 1);
        }

        return params.reduce(function(fragment, param) {
            return fragment.replace(/:[^/]+/.exec(fragment)[0], param);
        }, route) + queryString;
    }
});