code: function(match, esc) {
          if (/^(\n|\r\n|\r|\f)$/.test(esc)) { return ''; }
          var m = /^[0-9a-f]{1,6}/i.exec(esc);
          if (m) {
              var codePoint = parseInt(m[0], 16);
              if (String.fromCodePoint) {
                  return String.fromCodePoint(codePoint);
              } else {
                  // XXX No support for surrogates on old JavaScript engines.
                  return String.fromCharCode(codePoint);
              }
          }
          return esc;
      }
docs: Strip surrounding single/double quotes