function Parent(name) {
    this.name = name;
}

Parent.prototype.sayHello = function () {
    console.log(`I'm ${this.name}!`)
}

function Child(name, age) {
    Parent.call(this, name);
    this.age = age;
}

Child.prototype = Object.create(Parent.prototype)
Child.prototype.constructor = Child

Child.prototype.sayHello = function () {
    console.log(`I'm ${this.name} and ${this.age} years old!`)
}

Child.prototype.sayAge = function () {
    console.log(`I'm ${this.age} years old.`)
}

let parent = new Parent("John");
let child = new Child("Jane", 5);

parent.sayHello();
child.sayHello();