// source https://jsbin.com/gaborig

index.html

<p>Animal's name: <input type="text" id="f" size="10"></p>

<p>Animals sound: <input type="text" id="s" size="10"></p>

<button id="b" class="myButton">Introduce Animal</button>

<span id="write"></span>
<script id="jsbin-javascript">
var theButton = document.getElementById("b");
theButton.onclick = onButtonClick;

function Animal(name, sound) {
	this.name = name ? name : this.name;
  this.sound = sound ? sound : this.sound;
}

Animal.prototype.introduce = function() {
	return this.sound + "! I am a " + this.name;
}

Animal.prototype.name = "Pikachu";
Animal.prototype.sound = "Pika-pika";

function introduceAnimal( first, second ) { 
	var animal = new Animal(first, second);
  return animal.introduce();
}
 
function onButtonClick() {
  var box1 = document.getElementById("f").value;
  var box2 = document.getElementById("s").value;
  var result = introduceAnimal( box1, box2 );
  var place = document.getElementById("write");
  place.innerHTML = result;
}
</script>


<script id="jsbin-source-javascript" type="text/javascript">var theButton = document.getElementById("b");
theButton.onclick = onButtonClick;

function Animal(name, sound) {
	this.name = name ? name : this.name;
  this.sound = sound ? sound : this.sound;
}

Animal.prototype.introduce = function() {
	return this.sound + "! I am a " + this.name;
}

Animal.prototype.name = "Pikachu";
Animal.prototype.sound = "Pika-pika";

function introduceAnimal( first, second ) { 
	var animal = new Animal(first, second);
  return animal.introduce();
}
 
function onButtonClick() {
  var box1 = document.getElementById("f").value;
  var box2 = document.getElementById("s").value;
  var result = introduceAnimal( box1, box2 );
  var place = document.getElementById("write");
  place.innerHTML = result;
}
</script>

jsbin.gaborig.js

var theButton = document.getElementById("b");
theButton.onclick = onButtonClick;

function Animal(name, sound) {
	this.name = name ? name : this.name;
  this.sound = sound ? sound : this.sound;
}

Animal.prototype.introduce = function() {
	return this.sound + "! I am a " + this.name;
}

Animal.prototype.name = "Pikachu";
Animal.prototype.sound = "Pika-pika";

function introduceAnimal( first, second ) { 
	var animal = new Animal(first, second);
  return animal.introduce();
}
 
function onButtonClick() {
  var box1 = document.getElementById("f").value;
  var box2 = document.getElementById("s").value;
  var result = introduceAnimal( box1, box2 );
  var place = document.getElementById("write");
  place.innerHTML = result;
}