Fix: Error: Cannot serialize a BigInt error

The ‘Error: Cannot serialize a BigInt’ error occurs when trying to serialize BigInt values to JSON or other formats that don’t support BigInt natively, as JSON doesn’t have a native BigInt type.

How the Error Happens

❌ Error Scenario:

// ❌ This causes the error
const data = {
  id: 1234567890123456789012345678901234567890n, // ❌ BigInt value
  name: 'Big Number'
};

JSON.stringify(data); // ❌ Error: Cannot serialize a BigInt

✅ Quick Fix - Handle BigInt Serialization

Solution 1: Custom Replacer Function

// ✅ Use custom replacer to handle BigInt
const data = {
  id: 1234567890123456789012345678901234567890n,
  name: 'Big Number'
};

const jsonString = JSON.stringify(data, (key, value) =>
  typeof value === 'bigint' ? value.toString() : value
);

console.log(jsonString); // ✅ Serializes BigInt as string

Solution 2: Reviver Function for Deserialization

// ✅ Parse back to BigInt using reviver
const jsonString = '{"id":"1234567890123456789012345678901234567890","name":"Big Number"}';

const parsed = JSON.parse(jsonString, (key, value) =>
  /^\d+n$/.test(value) ? BigInt(value.slice(0, -1)) : value
);

console.log(parsed.id); // ✅ BigInt value restored

Solution 3: Convert BigInt Before Serialization

// ✅ Convert BigInt to string before serialization
function convertBigInt(obj) {
  return JSON.parse(JSON.stringify(obj, (key, value) =>
    typeof value === 'bigint' ? value.toString() : value
  ));
}

const data = {
  bigId: 9007199254740991n, // Larger than Number.MAX_SAFE_INTEGER
  name: 'Test'
};

const serializableData = convertBigInt(data);
const json = JSON.stringify(serializableData); // ✅ Works fine

Solution 4: Use Alternative Serialization Libraries

// ✅ Use libraries that support BigInt
// npm install lossless-json
import { stringify, parse } from 'lossless-json';

const data = {
  bigNumber: 123456789012345678901234567890n
};

// ✅ Serialize with BigInt support
const losslessJson = stringify(data);
const parsedData = parse(losslessJson); // ✅ BigInt preserved