Adding div element to body or document in JavaScript

Question

I am creating a light box in pure JavaScript. For that I am making an overlay. I want to add this overlay to body but I also want to keep the content on the page. My current

Answer 1

Using Javascript

var elemDiv = document.createElement('div');
elemDiv.style.cssText = 'position:absolute;width:100%;height:100%;opacity:0.3;z-index:100;background:#000;';
document.body.appendChild(elemDiv);

Using jQuery

$('body').append('
');