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)

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