absolute url

absolute.js

    function absolute(location, relative) {
        if (relative.startsWith("http://")
            || relative.startsWith("https://")
            || relative.startsWith("data:")) {
            return relative;
        }

        if (relative.startsWith("//")) {
            return location.protocol + relative;
        }

        var prefix = location.protocol + "//" + location.host + "/";

        if (relative.startsWith("/")) {
            return prefix + relative;
        }

        var paths = location.pathname.split("/");
        paths.pop();

        if (relative.startsWith(".")) {
            var relpaths = relative.split("/");
            var filename = relpaths.pop();

            for (var i = 0; i < relpaths.length; i++) {
                if (relpaths[i] == '.')
                    continue;
                if (relpaths[i] == "..")
                    paths.pop();
                else
                    paths.push(relpaths[i])
            }

            return prefix + paths.join("/") + "/" + filename;
        }

        return prefix + paths.join("/") + "/" + relative;
    }