Get Top Visible Line & Last Visible Line in HTML

I remember VB have great API to get reference of textbox first/top visible line position. I mostly use that to generate line number for my own text editor. Top visible line position is great reference and we can afford it in web development by using JavaScript.

I created this code in single line ternary, here it is:

<script type="text/javascript">
	topVisibleLine = (window.ActiveXObject)?parseInt(document.body.scrollTop):parseInt(window.pageYOffset);
	alert( "The top visible line now at " + topVisibleLine + "px" );
</script>

You can use this code to get reference for generated object position or just watch page position for prevent something.

And how about last visible line..? ..Simply add “screen height”

<script type="text/javascript">
	screenHeight = (window.ActiveXObject)?parseInt(document.body.offsetHeight):parseInt(window.innerHeight);
	topVisibleLine = (window.ActiveXObject)?parseInt(document.body.scrollTop):parseInt(window.pageYOffset);
	lastVisibleLine = topVisibleLine + screenHeight;
	alert( "The last visible line now at " + lastVisibleLine + "px" );
</script>

hope that’s help