Function to check if a DOM element is in the viewport

isInViewport.js

/*
@el = DOM element
@full = true | default: false // If true check if any part of the element is in the viewport
*/
function isInViewport (el, full) {
  var full = full || false;
  
  // check if the element is a jQuery object
  if (typeof jQuery === "function" && el instanceof jQuery) {
    el = el[0];
  }

  var rect = el.getBoundingClientRect();

  if (full) {
    return (
      top < (window.pageYOffset + window.innerHeight) &&
      left < (window.pageXOffset + window.innerWidth) &&
      (top + height) > window.pageYOffset &&
      (left + width) > window.pageXOffset
    );
  } else {
    return (
      rect.top >= 0 &&
      rect.left >= 0 &&
      rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /*or $(window).height() */
      rect.right <= (window.innerWidth || document.documentElement.clientWidth) /*or $(window).width() */
    );
  }
}