var unreserved = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_.~";
var reserved = "!*'();:@&=+$,/?%#[]";
var allowed = unreserved + reserved;
var hexchars = "0123456789ABCDEFabcdef";

function gethex(decimal) {
  return "%" + hexchars.charAt(decimal >> 4) + hexchars.charAt(decimal & 0xF);
 }

function encode(str) {
  var decoded = str;
  var encoded = "";

    for (var i = 0; i < decoded.length; i++ ) {
      var ch = decoded.charAt(i);
      if (unreserved.indexOf(ch) != -1) {
        encoded = encoded + ch;
      } else {
        var charcode = decoded.charCodeAt(i);
        if (charcode < 128) {
          encoded = encoded + gethex(charcode);
        }
        if (charcode > 127 && charcode < 2048) {
          encoded = encoded + gethex((charcode >> 6) | 0xC0);
          encoded = encoded + gethex((charcode & 0x3F) | 0x80);
        }
        if (charcode > 2047 && charcode < 65536) {
          encoded = encoded + gethex((charcode >> 12) | 0xE0);
          encoded = encoded + gethex(((charcode >> 6) & 0x3F) | 0x80);
          encoded = encoded + gethex((charcode & 0x3F) | 0x80);
        }
        if (charcode > 65535) {
          encoded = encoded + gethex((charcode >> 18) | 0xF0);
          encoded = encoded + gethex(((charcode >> 12) & 0x3F) | 0x80);
          encoded = encoded + gethex(((charcode >> 6) & 0x3F) | 0x80);
          encoded = encoded + gethex((charcode & 0x3F) | 0x80);
        }
      }
    }
	return encoded;
}