Route parameters and query strings in Express

Route Parameters vs Query Strings

Express gives you two ways to pass data in a URL: route parameters (part of the path) and query strings (after the ?).

Route parameters — req.params

app.get('/users/:id', (req, res) => {
  const { id } = req.params; // always a string
  const user = users.find(u => u.id === parseInt(id));
  if (!user) return res.status(404).json({ error: 'User not found' });
  res.json(user);
});

// Multiple params
app.get('/orgs/:orgId/users/:userId', (req, res) => {
  const { orgId, userId } = req.params;
  res.json({ orgId, userId });
});

Query strings — req.query

// GET /products?category=shoes&sort=price&limit=10
app.get('/products', (req, res) => {
  const { category, sort, limit = 20 } = req.query;
  // Filter/sort logic here
  res.json({ category, sort, limit: parseInt(limit) });
});

When to use which: Use route params for identifying a specific resource (/users/42). Use query strings for filtering, sorting, or pagination (/users?role=admin&page=2).

Route param values are always strings — always parse them when comparing to numbers. Query string values are also strings, including booleans: 'true' is not true.