What is JSON.parse() and JSON.stringify() in Node.js?

JSON.stringify(value, replacer, space) converts a JavaScript value (object, array, primitive) to a JSON string. The optional space parameter adds indentation for readability: JSON.stringify(obj, null, 2). It skips undefined, functions, and symbols. JSON.parse(string) parses a JSON string and returns the corresponding JavaScript value. If the string is invalid JSON, it throws a SyntaxError — always wrap in try/catch when parsing untrusted input: try { const data = JSON.parse(raw); } catch (e) { handle error }. In Express.js, express.json() middleware automatically calls JSON.parse on request bodies and sets req.body. For working with large JSON data efficiently, consider streaming parsers like stream-json rather than parsing the entire payload into memory at once.