When the four major browsers chrome, firefox, ie, and opera have scroll bars on the web page:
clientHeight refers to the visible height in each browser
When the actual content height of the web page is greater than clientHeight, chrome, firefox, ie, and opera all set scrollHeight and offsetHeight as the height of the web page content, specifically the actual content height, scroll bar height, and web page border height
When the actual content height of the web page is less than clientHeight, chrome, firefox, ie, and opera all set scrollHeight to clientHeight.
chrome, firefox, and opera all set offsetHeight to the actual height of the web page content, specifically the actual content. Height The height of the scroll bar is the height of the web page border. IE11 sets offsetHeight to ClientHeight