toStringMethod.js

function User(firstName, lastName, age) {
  this.firstName = firstName,
    this.lastName = lastName,
    this.age = age
}

const Akash = new User('Akash', 'Rajvanshi', 22);

User.prototype.toString = function getDetails() {
  return `I am ${this.firstName} ${this.lastName} (${this.age})`
}
console.log(Akash.toString()) // I am Akash Rajvanshi (22)