Get window(aka viewport) width and height.

viewport.js

/**
 * Get window/viewport width and height. The window.innerWidth value includes the scrollbar,
 * and document.documentElement.clientWidth/document.body.clientWidth doesn't include.
 * Compatibility: IE6+ and other modern browsers
 */
function winW() {
  return window.innerWidth || document.documentElement.clientWidth;
}

function winH() {
  return window.innerHeight || document.documentElement.clientHeight;
}