JSFiddle - React, Tailwind, and code Playground

JavaScript

function Animal(obj){
	this.name = obj.name;
	this.age = obj.age;
	this.al = function(){
		alert(this.name + ' живут ' + this.age + ' лет');
	}
}

var dog = new Animal({name:'dog', age: 15});
dog.al();
dog.al = function(){
	alert(this.name + ' живут ' + (this.age+10) + ' лет');
}
dog.al();