How do I let clients select specific fields in a Node.js API?
Use a fields query param. const fields = req.query.fields ? req.query.fields.split(',').join(' ') : null. Then .select(fields). Whitelist selectable fields to prevent exposing sensitive data like passwordHash.
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More FAQs in Filtering and Sorting in Node.js APIs: A Complete Guide
Use query params. Build a filter object based on which params are present. Whitelist the fields users can filter by to prevent query injection. Pass the filter to Model.find(filter).
Use sortBy and order query params. Whitelist sortable fields to prevent errors and abuse. const sortBy = allowedSorts.includes(req.query.sortBy) ? req.query.sortBy : 'createdAt'. Use .sort({ [sortBy]: order }).
To prevent query injection (users setting arbitrary filter fields to probe your data) and errors (users sorting by a field that does not exist). Whitelisting limits the surface and keeps the API predictable.
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