code: function getElementHeight (element) {
      var clone = element.cloneNode(true)
      clone.style.cssText = 'visibility: hidden; display: block; margin: -999px 0'
  
      var height = (element.parentNode.appendChild(clone)).clientHeight
      element.parentNode.removeChild(clone)
  
      return height
    }
docs: Clone an element outside the screen to safely get its height, then destroy it.