javascript-How to detect scroll event in iframe?

Question

I have a problem when I try add event scroll with iframe tage. generally, I use scroll event with div tag It was working well. but when I add scroll event in iframe tag to detect user scroll pdf page, It was not working. why cannot I access html elements in iframe?, I have code inspect below:

and I try to add javascript scroll event with iframe :

HTML Code:

<iframe id="myframe" src="doc.pdf"></iframe>

JavaScript Code:

document.getElementById('myframe').onscroll = function(){
	 	alert('scrolling page');
};

Answer 1

An iframe does not have a scroll method, the document of the iframe does - you need to reference the inner document rather than your <iframe> tag.

You can reference it with iframe.contentDocument:

var iframe = document.getElementById('frame');

iframe.contentDocument.body.innerHTML = 'a<br>a<br>a<br>a<br>a<br>a<br>a<br>a<br>a<br>a<br>';

iframe.contentDocument.addEventListener('scroll', function(event) {
  console.log(event);
}, false);

<iframe id="frame"></iframe>

See: https://developer.mozilla.org/en-US/docs/Web/API/HTMLIFrameElement for more information

Answer 2

JavaScript provide us onscroll as an attribute which passes parameters (Can be a function). But we got iframe here, try the following code snippet (jQuery).

$("#yourFrameId").load(function () {
     var iframe = $("#yourFrameId").contents();

    $(iframe).scroll(function () { 
        //your code here
    });
});