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)
const 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