<html>
  <head>
    <style style="display: block; white-space: pre;" contenteditable>
      * {
        transition: all linear 0.5s;
      }
      html {
        background: red;
      }
    </style>
  </head>
  <body>
    
  </body>
</html>
document.addEventListener('keydown', event => {
  if (event.key === 'Enter') {
    document.execCommand('insertLineBreak')
    event.preventDefault()
  }
})
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