Status code conventions in Express

Introduction

Status codes tell the browser or client what happened with a request. They help show if things worked or if there was a problem.

When sending a response after a user requests a webpage or data.

When an error happens and you want to tell the client what went wrong.

When a user sends data to your server and you want to confirm it was saved.

When redirecting a user to a different page or URL.

When a requested resource is not found on the server.

Syntax

Express

res.status(code).send(body)

res is the response object in Express.

status(code) sets the HTTP status code for the response.

Examples

Sends a success message with status code 200.

Express

res.status(200).send('OK')

Tells the client the requested page was not found.

Express

res.status(404).send('Not Found')

Indicates a problem happened on the server.

Express

res.status(500).send('Server Error')

Confirms a new resource was created and sends its data.

Express

res.status(201).json({ id: 123 })

Sample Program

This Express app shows how to use status codes for different routes: success (200), not found (404), and created (201).

Express

import express from 'express';
const app = express();

app.get('/', (req, res) => {
  res.status(200).send('Welcome to the homepage!');
});

app.get('/notfound', (req, res) => {
  res.status(404).send('Page not found');
});

app.post('/create', (req, res) => {
  // pretend we create something here
  res.status(201).json({ message: 'Resource created' });
});

app.listen(3000, () => {
  console.log('Server running on http://localhost:3000');
});

Important Notes

Always use the correct status code to help clients understand the response.

Common codes: 200 (OK), 201 (Created), 400 (Bad Request), 404 (Not Found), 500 (Server Error).

You can chain res.status() with other response methods like send() or json().

Summary

Status codes tell clients what happened with their request.

Use res.status(code) in Express to set the code.

Pick codes that match the situation for clear communication.