API Filtering & Sorting
Build flexible filtering and sorting systems that handle complex queries efficiently.
Query Parameter Syntax
GET /products?category=electronics&price[gte]=100&price[lte]=500&sort=-price,name
Implementation (Node.js)
javascriptconst allowedFilters = ['category', 'status', 'price', 'createdAt']; const allowedSorts = ['name', 'price', 'createdAt']; app.get('/products', async (req, res) => { const filter = {}; const sort = {}; // Parse filters for (const [key, value] of Object.entries(req.query)) { if (key === 'sort') continue; const match = key.match(/^(\w+)\[(\w+)\]$/); if (match) { const [, field, operator] = match; if (!allowedFilters.includes(field)) continue; filter[field] = { [`$${operator}`]: parseValue(value) }; } else if (allowedFilters.includes(key)) { filter[key] = value; } } // Parse sort if (req.query.sort) { for (const field of req.query.sort.split(',')) { const direction = field.startsWith('-') ? -1 : 1; const name = field.replace(/^-/, ''); if (allowedSorts.includes(name)) sort[name] = direction; } } const products = await Product.find(filter).sort(sort); res.json({ data: products }); }); function parseValue(value) { if (value === 'true') return true; if (value === 'false') return false; if (!isNaN(value)) return Number(value); return value; }
Filter Operators
| Operator | Meaning | Example |
|---|---|---|
| eq | Equals | ?status=active |
| ne | Not equals | ?status[ne]=deleted |
| gt/gte | Greater than | ?price[gte]=100 |
| lt/lte | Less than | ?price[lte]=500 |
| in | In array | ?status[in]=active,pending |
| like | Contains | ?name[like]=phone |
Security
- Whitelist allowed filter fields
- Validate input types per field
- Index frequently-filtered columns
- Limit query complexity
- Prevent SQL/NoSQL injection
Best Practices
- Support common operators
- Cache filter option lists
- Monitor query performance
- Provide sensible defaults
