问题
I need to determine if an element in an iframe is visible on the screen. (if it is on the visible part of the screen) I mean the page can be very long and user must scroll to see the element
index.html:
<html>
...
...
<iframe src="iframe.html" />
...
...
</html>
iframe.html:
<html>
...
...
<div id="element"></div>
....
...
<script type="text/javascript">
var el = document.getElementById('element');
if (isElementVisible(el)) {
// do something
}
</script>
</html>
How to write such a function isElementVisible()?
回答1:
Here is an example of what you are trying to achieve.
Working example
Just the iframe
Basically, this is the function that should go inside your iframe:
function isElementVisible(element)
{
var elementPosition = element.offset().top;
var currentScroll = window.parent.$("iframe").contents().scrollTop();
var screenHeight = window.parent.$("iframe").height();
var visibleArea = currentScroll + screenHeight;
return (elementPosition < visibleArea);
}
Trigger your checks with a scroll event handler.
$(window).scroll(function(){
if( isElementVisible( element ) )
// Perform your code.
});
This works assuming the iframe is in the same domain as the parent frame. I use jQuery for convenience.
来源：https://stackoverflow.com/questions/15250235/determine-if-an-element-in-an-iframe-is-visible-on-the-screen