Right now we use codemirror's JavaScript mode on the website but there's a JSX mode now so we should start using that instead.

if (!byUnit) return pos + dir;
    do pos += dir;
    while (pos > 0 && isExtendingChar.test(line.text.charAt(pos)));
    return pos;
  }
  
  
  
  
  
  
  function moveVisually(line, start, dir, byUnit) {