The length property contains the number of objects that are in the images[] array.
<html>
<h2>A Circle</h2>
<img src="http://www.java2s.com/style/logo.png">
<h2>A Square</h2>
<img src="http://www.java2s.com/style/logo.png"><br>
<script language="JavaScript">
<!--
document.write(document.images.length," image objects.");
-->
</script>
</html>