Glitch has a debugger tool (which currently only works in the Google Chrome browser) that you can access via the editor's Logs tray.
1. Click on the "Tools" button on the lower-right side of the project editor.
2. Click the "Logs" button on top of the Container Tools menu.
3. Click the "Debugger" button on the top of the open "Logs" tray.
For security reasons, Chrome does not allow us to open the debugger through a normal button or link, so you'll need to manually copy and paste the debugger URL manually. Glitch will provide this link by opening a new tab when you click the "Debugger" button (step 3, above).
Paste the link into a new browser window or tab, and you'll have a Chrome Developer Tools window where you can debug the Node.js parts of your app.