js determines whether the web page in the iframe scrolls to the bottom and triggers the event_javascript skills

There was a need before to determine whether the web page in the iframe scrolled to the bottom to trigger an event. I found a lot of information on the Internet that said it was under the current page, so I simply did some research on my own and found a solution.

clientHeight: the height of this element, the height of the entire space occupied

offsetHeight: refers to the height of the element content

scrollTop: can be understood as the length that the scroll bar can scroll

or less Is the source code