gistfile1.js

var msg = JSON.stringify( state );

var getUTF8Size = function( str ) {
  var sizeInBytes = str.split('')
    .map(function( ch ) {
      return ch.charCodeAt(0);
    }).map(function( uchar ) {
      // The reason for this is explained later in
      // the section “An Aside on Text Encodings”
      return uchar < 128 ? 1 : 2;
    }).reduce(function( curr, next ) {
      return curr + next;
    });

  return sizeInBytes;
};

var msgSize = getUTF8Size( msg ); // 410 bytes