Answers for "document.getElementById(...).getContext is not a function"

document.getElementById(...).getContext is not a function

/* 
	.getContext() it's only a property method of canvas, 
	its not a property method of div or else
*/

Uncaught TypeError: document.getContext is not a function

<script language="Javascript" type="text/Javascript" src="pong.js" defer></script>