https://ibsindia.org/IBSAF/pop.js

1// JavaScript Document
2
3function toggle(div_id) {
4	var el = document.getElementById(div_id);
5	if ( el.style.display == 'none' ) {	el.style.display = 'block';}
6	else {el.style.display = 'none';}
7}
8function blanket_size(popUpDivVar) {
9	if (typeof window.innerWidth != 'undefined') {
10		viewportheight = window.innerHeight;
11	} else {
12		viewportheight = document.documentElement.clientHeight;
13	}
14	if ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) {
15		blanket_height = viewportheight;
16	} else {
17		if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) {
18			blanket_height = document.body.parentNode.clientHeight;
19		} else {
20			blanket_height = document.body.parentNode.scrollHeight;
21		}
22	}
23	var blanket = document.getElementById('blanket');
24	blanket.style.height = blanket_height + 'px';
25	var popUpDiv = document.getElementById(popUpDivVar);
26	popUpDiv_height=blanket_height/2-200;//100 is half popup's height
27	popUpDiv.style.top = popUpDiv_height + 'px';
28}
29function window_pos(popUpDivVar) {
30	if (typeof window.innerWidth != 'undefined') {
31		viewportwidth = window.innerHeight;
32	} else {
33		viewportwidth = document.documentElement.clientHeight;
34	}
35	if ((viewportwidth > document.body.parentNode.scrollWidth) && (viewportwidth > document.body.parentNode.clientWidth)) {
36		window_width = viewportwidth;
37	} else {
38		if (document.body.parentNode.clientWidth > document.body.parentNode.scrollWidth) {
39			window_width = document.body.parentNode.clientWidth;
40		} else {
41			window_width = document.body.parentNode.scrollWidth;
42		}
43	}
44	var popUpDiv = document.getElementById(popUpDivVar);
45	window_width=window_width/2-250;//250 is half popup's width
46	popUpDiv.style.left = window_width + 'px';
47}
48function popup(windowname) {
49	blanket_size(windowname);
50	window_pos(windowname);
51	toggle('blanket');
52	toggle(windowname);		
53}