How to pass a replacer function to JSON.stringify() to customize the serialization in TypeScript

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class User {
  userid: number;
  username: string;
  age: number;
  password: string; // should not be serialized

  constructor(userid: number, username: string, age: number, password: string) {
    this.userid = userid;
    this.username = username;
    this.age = age;
    this.password = password;
  }
}

const user: User = new User(9382732, "A AI", 52, "ah@746Eo87R!");

// Convert class instance to JSON
const jsonString: string = JSON.stringify(user, (key, value) => {
  if (key === "password") {
    return undefined; // Exclude this key
  }
  return value;
});

console.log("JSON String:", jsonString);



/*
run:

"JSON String:",  "{"userid":9382732,"username":"A AI","age":52}" 

*/

 



answered Dec 7, 2025 by avibootz
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