How to fix SyntaxError: Unexpected token < in JSON at position 0 (express.json() failed) in Node.js

// WRONG - typo in URL or route doesn't exist
const response = await fetch('/api/usrs'); // should be /api/users

// CORRECT
const response = await fetch('/api/users');

// With fetch
const response = await fetch('/api/users');
const text = await response.text();
console.log('Response:', text);
const data = JSON.parse(text); // or response.json()

// With axios
const response = await axios.post('/api/users', data);
console.log('Response:', response.data);

const express = require('express');
const app = express();

// Middleware BEFORE routes
app.use(express.json());

// Route handler AFTER middleware
app.post('/api/users', (req, res) => {
  // req.body is now parsed JSON
  console.log(req.body);
  res.json({ success: true });
});

app.listen(3000);

// With fetch
const response = await fetch('/api/users', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({ name: 'John' }),
});

// With axios
const response = await axios.post('/api/users', { name: 'John' }, {
  headers: { 'Content-Type': 'application/json' },
});

// Check if data is valid JSON
const data = { name: 'John' };
try {
  const json = JSON.stringify(data);
  console.log('Valid JSON:', json);
} catch (e) {
  console.error('Invalid JSON:', e);
}

// When receiving, wrap in try-catch
const response = await fetch('/api/users');
const data = await response.json().catch(err => {
  console.error('Parse error:', err);
  throw new Error('Failed to parse response as JSON');
});

# Stop the server
Ctrl+C

# Restart
node server.js
# or with npm scripts
npm start