How to know scroll to element is done in Javascrip

问题:

I am using Javascript method Element.scrollIntoView()
https://developer.mozilla.org/en-US/docs/Web/API/Element/scrollIntoView

Is there any way I can get to know when the scroll is over. Say there was an animation, or I have set {behavior: smooth}.

I am assuming scrolling is async and want to know if there is any callback like mechanism to it.

回答1:

You can use IntersectionObserver, check if element .isIntersecting at IntersectionObserver callback function

const element = document.getElementById("box");

const intersectionObserver = new IntersectionObserver((entries) => {
  let [entry] = entries;
  if (entry.isIntersecting) {
    setTimeout(() => alert(`${entry.target.id} is visible`), 100)
  }
});
// start observing
intersectionObserver.observe(box);

element.scrollIntoView({behavior: "smooth"});

body {
  height: calc(100vh * 2);
}

#box {
  position: relative;
  top:500px;
}

<div id="box">
box
</div>

回答2:

There is no scrollEnd event, but you can listen for the scroll event and check if it is still scrolling the window:

var scrollTimeout;
addEventListener('scroll', function(e) {
    clearTimeout(scrollTimeout);
    scrollTimeout = setTimeout(function() {
        console.log('Scroll ended');
    }, 100);
});

回答3:

i'm not an expert in javascript but i made this with jQuery. i hope it helps

$("#mybtn").click(function() {
    $('html, body').animate({
        scrollTop: $("div").offset().top
    }, 2000);
});

$( window ).scroll(function() {
  $("div").html("scrolling");
  if($(window).scrollTop() == $("div").offset().top) {
    $("div").html("Ended");
  }
})

body { height: 2000px; }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<button id="mybtn">Scroll to Text</button>
<br><br><br><br><br><br><br><br>
<div>example text</div>