经过数小时的挫折，我搬走了

After many hours of frustration, I moved

const SerialPort = require('serialport');

从应该由webpack捆绑到index.html的javascript文件中:

from javascript file which is supposed to be bundled by webpack to index.html:

<script>
  const SerialPort = require('serialport');
</script>
<script src="dist/bundle.js"></script>

SerialPort现在可以识别了.

SerialPort is now recognized.

此外，似乎webpack-dev-server在Electron和serialport上不能很好地工作.我必须启动完整的电子应用程序.

Also, it seems like webpack-dev-server doesn't work very well with Electron and serialport. I have to launch full electron app.