index.html

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8">
  <title>Notepad</title>

  <style>
    textarea {
      width: 100vw;
      height: 100vh;
      padding: 0;
      border: 0;
      outline: 0;
      margin: 0;
      position: absolute;
      top: 0;
      left: 0;
    }
  </style>
</head>

<body>
  <textarea id="cmdIn"></textarea>
  <script>
    const {
      ipcRenderer
    } = require('electron')
    const buffer = document.getElementById('cmdIn')
    let prompt = ""

    function updateBuffer(data) {
      buffer.value = buffer.value + data;
    }

    window.addEventListener('keypress', (e) => {
      if (e.keyCode === 13) {
        let cmd = cmdIn.value.split('\n').pop().split(prompt).slice(1).join()
        if (cmd && cmd.length > 0) {
          ipcRenderer.send('msg', cmd)
        } else {
          buffer.value = buffer.value.split("\n").slice(0,-1).join("\n") + "\n" + prompt
        }
      }
    })

    ipcRenderer.on('asynchronous-reply', (event, arg) => {
      updateBuffer(arg)
    })

    ipcRenderer.on('cwd', (event, arg) => {
      prompt = arg + "$ "
      updateBuffer(prompt)
    })

    ipcRenderer.send('cwd')
  </script>
</body>

</html>