JSON.stringify() Replacer

JSON Replacer

The replacer argument in JSON.stringify() filters or transforms values. Pass an array of key names or a function.

Example

const data = { id: 1, name: "Alice", password: "secret", age: 30 };

// Array replacer — include only these keys
JSON.stringify(data, ["id", "name", "age"]);
// {"id":1,"name":"Alice","age":30}

// Function replacer — custom transformation
JSON.stringify(data, (key, value) => {
  if (key === "password") return undefined; // Omit passwords
  if (typeof value === "number") return value * 2; // Double numbers
  return value;
});
// {"id":2,"name":"Alice","age":60}

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Pro Tip

Use a function replacer to sanitize sensitive fields like passwords and tokens before JSON serialization.

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