code: function(escapable) {
    var i;
    var unrolled = {};
    var c = [];
    for (i = 0; i < 65536; i++) {
      c.push( String.fromCharCode(i) );
    }
    escapable.lastIndex = 0;
    c.join('').replace(escapable, function(a) {
      unrolled[ a ] = '\\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);
      return '';
    });
    escapable.lastIndex = 0;
    return unrolled;
  }
docs: This may be quite slow, so let's delay until user actually uses bad characters.