How do I filter an Express API?
Build a filter object from query params. if (req.query.role) filter.role = req.query.role. Pass the filter to User.find(filter). Whitelist allowed filters to prevent arbitrary queries.
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More FAQs in API Pagination, Filtering, and Sorting in Express
Use skip and limit: User.find().skip(parseInt(req.query.skip) || 0).limit(Math.min(parseInt(req.query.limit) || 20, 100)). Always cap limit (e.g., max 100) to prevent abuse.
Instead of skip (which scans skipped docs), use a cursor like the last createdAt. Find documents where createdAt is less than the cursor. Faster for very large collections because MongoDB uses an index.
Use sortBy and order query params. const sortBy = req.query.sortBy || 'createdAt'; const order = req.query.order === 'asc' ? 1 : -1. User.find().sort({ [sortBy]: order }). Whitelist sortable fields.
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