Untitled

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
</head>
<body>

<script id="jsbin-javascript">
var counter = function( start ) {
  this.count = start;

  this.add = function() {
    this.count++;
  };

  this.display = function() {
    console.log( this.count );
  };
}

var a = new counter( 2 );
var b = new counter( 11 );
a.display();
b.display();
a.add();
a.add();
a.display();
b.display();
</script>


<script id="jsbin-source-javascript" type="text/javascript">var counter = function( start ) {
  this.count = start;

  this.add = function() {
    this.count++;
  };

  this.display = function() {
    console.log( this.count );
  };
}

var a = new counter( 2 );
var b = new counter( 11 );
a.display();
b.display();
a.add();
a.add();
a.display();
b.display();</script></body>
</html>