Simpler JS hex serialization

hex.js

/* Damn simple hex parser, with utf8 convenience functions */
var utf8={
        decode: function(s){
            return decodeURIComponent(escape(s));
        },
        encode: function(s){
            return unescape(encodeURIComponent(s));
        }
    },
    hex={
        decode: function(str){
            var r='', i=0, l=str.length;
            while(i<l)
                r += String.fromCharCode(parseInt(str.substring(i, i+=2), 16));
            return r;
        },
        encode: function(str){
            var r='', i=0, l=str.length;
            while(i<l) r += str.charCodeAt(i++).toString(16);
            if(r.length>l*2) // raise on multibyte characters
                throw 'Invalid input, only byte strings are allowed.';
            return r;
        },
    };