Debug Node Apps in The Browser! Node Tips

When things go horribly wrong in your code, console.log can only get you so far.

I often use the debugger statement in normal JavaScript apps to inspect, stop and step through my code.

Wouldn't it be great if you could debug your Node apps as easily?

Well, obviously, you're about to learn how.

Let's level up and explore a more efficient way to debug your Node.js applications using the --inspect flag.

Let's look at a short code example to see it in action.

Suppose we have a simple Express app with a debugger statement we want to trigger:

// app.js
const express = require("express");
const app = express();
const port = 3000;

app.get("/", (req, res) => {
  debugger; // <-- We want to get this to open in the browser 
  res.send("hello world");
});

app.listen(port, () => {
  console.log(`Example app listening on port ${port}`);
});

When running a Node.js application, appending the --inspect flag to your command initiates a debugging session.

It's simple to use:

node --inspect app.js

This will return your debugging session with a URL with the shape of ws://127.0.0.1:9229/some-uid like you can see here: Screenshot of the result of running node --inspect app.js

Open chrome://inspect in a Chromium-based browser or edge://inspect in Edge. You should see an option to "inspect" your application as shown below:

Screenshot of "chrome://inspect" tab

Once you inspect the element, it will open a console like this: Screenshot of the debugging console

Notice that you can see the normal output that you would see in your terminal here now too (so you can see what you log in your app here too).

Then if we hit the http://localhost:3000/ route, we should see the debugger being hit: Screenshot of the debugger being triggered in the console

Now you can use the debugger just like you would in a regular JS application. Step over the code, inspect the variables and make your life much easier! 📈


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Avatar for Niall Maher

Written by Niall Maher

Founder of Codú - The web developer community! I've worked in nearly every corner of technology businesses; Lead Developer, Software Architect, Product Manager, CTO and now happily a Founder.

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