JSFiddle - React, Tailwind, and code Playground

HTML

<script>
var FirstClass = function() {
  this.a = 1;
}

FirstClass.prototype.method_1 = function() {
  return 1;
}

var SecondClass = function() {
  this.b = 2;
}

SecondClass.prototype = new FirstClass();
SecondClass.prototype.constructor = SecondClass;

SecondClass.prototype.method_2 = function() {
  return 2;
}

var obj = new SecondClass();

alert(obj.a);
alert(obj.method_1());

alert(obj.b);
alert(obj.method_2());
</script>