<script> var url = new URL(location.href) const port = new URLSearchParams(url.search).get("port") const ipcRenderer = require('electron').ipcRenderer let count = 0 function checkFinish() { count++ if (count === 2) { ipcRenderer.send('websocket-success') } } var conn = new WebSocket(`ws://127.0.0.1:${port}/websocket`) conn.onopen = data => conn.send('foo') conn.onmessage = wsMsg function wsMsg(msg) { if (msg.data === 'bar') { checkFinish() } else { ipcRenderer.send('fail') } } fetch(`http://127.0.0.1:${port}/`).then(() => { checkFinish() }) </script>