How to get the the value for a form element using JavaScript by ID

If you have a text input box with ID age and you want to obtain the value for the text box via JavaScript use the JavaScript function getElementById() to get the value

Html input text box

<input type="text" name="age" id="age" value="12" />

JavaScript function

	<script type="text/javascript">
 
	var age = document.getElementById('age').value;
 
	</script>