Express 5: req.body is undefined (not {}) when no body parser ran — destructuring req.body throws
Mount the parsers and guard the access:
const app = express()
app.use(express.json())
app.use(express.urlencoded({ extended: false }))
app.post('/user', (req, res) => {
// before: const { name } = req.body
const { name } = req.body ?? {}
if (!name) return res.status(400).json({ error: 'name required' })
res.status(201).json({ name })
})
With schema validation, parse req.body ?? {} (or reject when req.body === undefined) instead of assuming an object.
Symptom
After upgrading to Express 5, handlers that do const { name } = req.body throw a TypeError (cannot destructure undefined) for requests with no body, a non-JSON content type, or on routes where no parser is mounted. Express 4 code that relied on req.body always being an object breaks. Wrong assumption: req.body defaults to {}.
Cause
Express 5 (5.1.0 tagged latest on npm 2025-03-31) no longer initializes req.body; it stays undefined unless a body-parsing middleware parsed the request. (body-parser 2.x, used by express.json()/express.urlencoded(), also leaves it undefined when the content type doesn't match.)
Verify
curl -X POST localhost:3000/user (no body) returns 400, not a 500 with a destructuring TypeError.
Sources
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