Need to find height of hidden div on page (set to display:none)

Answer 1

A workaround is to set the height to 0

.hidden { 
  height: 0; 
  overflow: hidden; 
}

Then to get the elements scrollHeight.

document.querySelector('.hidden').scrollHeight

The scrollHeight will correctly give you the height though the element does not appear. I don't think it affects element flow either.

Example: https://jsfiddle.net/de3vk8p4/7/
Reference: https://developer.mozilla.org/en-US/docs/Web/API/CSS_Object_Model/Determining_the_dimensions_of_elements#How_big_is_the_content.3F