Javascript Will Assign And Test A Variable In The Same Statement

code-1.js

// Get the page header.
var objHeader = document.getElementById( "header" );

// Check to see if the header exists.
if (objHeader){

	... more code here ...

}

code-2.htm

<!-- HTLM header / span. -->
<div id="header"><span>Title Span</span></div>

<script type="text/javascript">

	// Define the variables as null.
	var objHeader = null;
	var objHeaderSpan = null;


	// In this IF statement, assign the variables and
	// check to see if they result in valid objects.
	if (
		(objHeader = document.getElementById( "header" )) &&
		(objHeaderSpan = objHeader.childNodes[ 0 ])
		){

		// If we have gotten this far, then we have assigned
		// DOM elements to both objHeader and objHeaderSpan
		// and we KNOW that they exist. Aler inner HTML.
		alert( objHeaderSpan.innerHTML );

	}

</script>