The author of the following code intended "You are on the Home page" to appear in a dialog when the button is clicked. It doesn't work this way. Why not?

gistfile1.html

<button>Which page am I on?</button>

<script>
var Page = {
   title: 'Home',
   init: function() {
      document.querySelector('button').onclick = function () {
         alert('You are on the ' + this.title + ' page');
      };
   }
};

Page.init();
</script>