eggheadio-projects/understand-javascript-s-this-keyword-in-depth: null

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>Plunker</title>
</head>
<body>
	<script>
    // Allows Plunker to display logs in preview panel 
    // for better in-browser experience
    var originalConsoleLog = console.log
    console.log = function() {
      originalConsoleLog.apply(console, arguments)
      var args = Array.prototype.slice.call(arguments).map(JSON.stringify);
      document.body.innerText += args.join(' ') + '\n';
      document.body.style['fontFamily'] = 'monospace';
      document.body.style['fontSize'] = '1.5em';
    };
  </script>
  <script src="script.js"></script>
</body>
</html>

function Person(firstName, lastName) {
  console.log(this);
  this.firstName = firstName;
  console.log(this);
  this.lastName = lastName;
  console.log(this);
  
  // return this;
}

const person = new Person("Jane", "Doe");