how to make function in javascript for class code example

Example 1: javascript class

class ClassMates{
	constructor(name,age){
    	this.name=name;
      	this.age=age;
    }
  	displayInfo(){
    	return this.name + "is " + this.age + " years old!";
    }
}

let classmate = new ClassMates("Mike Will",15);
classmate.displayInfo();  // result: Mike Will is 15 years old!

Example 2: class in javascript

class Car {
    constructor(name, year) {
        this.name = name;
        this.year = year;
    }
    age(x) {
        return x - this.year;
    }
}

let date = new Date();
let year = date.getFullYear();

let myCar = new Car("Ford", 2014);
document.getElementById("class1").innerHTML = "My car is " + myCar.age(year) + " years old.";