Create a Background overlay in javascript

JavaScript Plugins 1

//overlay.js

var myOverlay = document.createElement('div');
myOverlay.id = "overlay";
document.body.appendChild(myOverlay);

//Setup Overlay Styles
myOverlay.style.position = 'absolute';
myOverlay.style.top = 0;
myOverlay.style.backgroundColor = 'rgb(0,0,0,0.7)';
myOverlay.style.cursor = "pointer";

//Resize and position overlay
myOverlay.style.width = window.innerWidth + "px";
myOverlay.style.height = window.innerHeight + "px";
myOverlay.style.top = window.pageYOffset + "px";
myOverlay.style.left = window.pageXOffest + "px";