How to check if element is visible after scrolling?

This should do the trick:

function isScrolledIntoView(elem)
{
    var docViewTop = $(window).scrollTop();
    var docViewBottom = docViewTop + $(window).height();

    var elemTop = $(elem).offset().top;
    var elemBottom = elemTop + $(elem).height();

    return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}

Simple Utility Function This will allow you to call a utility function that accepts the element you're looking for and if you want the element to be fully in view or partially.

function Utils() {

}

Utils.prototype = {
    constructor: Utils,
    isElementInView: function (element, fullyInView) {
        var pageTop = $(window).scrollTop();
        var pageBottom = pageTop + $(window).height();
        var elementTop = $(element).offset().top;
        var elementBottom = elementTop + $(element).height();

        if (fullyInView === true) {
            return ((pageTop < elementTop) && (pageBottom > elementBottom));
        } else {
            return ((elementTop <= pageBottom) && (elementBottom >= pageTop));
        }
    }
};

var Utils = new Utils();

Usage

var isElementInView = Utils.isElementInView($('#flyout-left-container'), false);

if (isElementInView) {
    console.log('in view');
} else {
    console.log('out of view');
}

WebResourcesDepot wrote a script to load while scrolling that uses jQuery some time ago. You can view their Live Demo Here. The beef of their functionality was this:

$(window).scroll(function(){
  if  ($(window).scrollTop() == $(document).height() - $(window).height()){
    lastAddedLiveFunc();
  }
});

function lastAddedLiveFunc() { 
  $('div#lastPostsLoader').html('<img src="images/bigLoader.gif">');
  $.post("default.asp?action=getLastPosts&lastPostID="+$(".wrdLatest:last").attr("id"),
    function(data){
        if (data != "") {
          $(".wrdLatest:last").after(data);         
        }
      $('div#lastPostsLoader').empty();
    });
};

The easiest solution I found for this is Intersection Observer API:

var observer = new IntersectionObserver(function(entries) {
    if(entries[0].isIntersecting === true)
        console.log('Element has just become visible in screen');
}, { threshold: [0] });

observer.observe(document.querySelector("#main-container"));

I have such a method in my application, but it does not use jQuery:

/* Get the TOP position of a given element. */
function getPositionTop(element){
    var offset = 0;
    while(element) {
        offset += element["offsetTop"];
        element = element.offsetParent;
    }
    return offset;
}

/* Is a given element is visible or not? */
function isElementVisible(eltId) {
    var elt = document.getElementById(eltId);
    if (!elt) {
        // Element not found.
        return false;
    }
    // Get the top and bottom position of the given element.
    var posTop = getPositionTop(elt);
    var posBottom = posTop + elt.offsetHeight;
    // Get the top and bottom position of the *visible* part of the window.
    var visibleTop = document.body.scrollTop;
    var visibleBottom = visibleTop + document.documentElement.offsetHeight;
    return ((posBottom >= visibleTop) && (posTop <= visibleBottom));
}

Edit : This method works well for I.E. (at least version 6). Read the comments for compatibility with FF.

The Javascript code could be written as :

window.addEventListener('scroll', function() {
    var element = document.querySelector('#main-container');
    var position = element.getBoundingClientRect();

    // checking whether fully visible
    if(position.top >= 0 && position.bottom <= window.innerHeight) {
        console.log('Element is fully visible in screen');
    }

    // checking for partial visibility
    if(position.top < window.innerHeight && position.bottom >= 0) {
        console.log('Element is partially visible in screen');
    }
});

and in react js written as:

    componentDidMount() {
        window.addEventListener('scroll', this.isScrolledIntoView);
    }

    componentWillUnmount() {
        window.removeEventListener('scroll', this.isScrolledIntoView);
    }
  
  isScrolledIntoView() {
        var element = document.querySelector('.element');
        var position = element.getBoundingClientRect();

        // checking whether fully visible
        if (position.top >= 0 && position.bottom <= window.innerHeight) {
            console.log('Element is fully visible in screen');
        }
        // checking for partial visibility
         if (position.top < window.innerHeight && position.bottom >= 0) {
            console.log('Element is partially visible in screen');
         }
    }

There are over 30 answers to this question, and none of them use the amazingly simple, pure JS solution that I have been using. There is no need to load jQuery just to solve this, as many others are pushing.

In order to tell if the element is within the viewport, we must first determine the elements position within the body. We do not need to do this recursively as I once thought. Instead, we can use element.getBoundingClientRect().

pos = elem.getBoundingClientRect().top - document.body.getBoundingClientRect().top;

This value is the Y difference between the top of the object and the top of the body.

We then must tell if the element is within view. Most implementations ask if the full element is within the viewport, so this is what we shall cover.

First of all, the top position of the window is: window.scrollY.

We can get the bottom position of the window by adding the window's height to its top position:

var window_bottom_position = window.scrollY + window.innerHeight;

Lets create a simple function for getting the element's top position:

function getElementWindowTop(elem){
    return elem && typeof elem.getBoundingClientRect === 'function' ? elem.getBoundingClientRect().top - document.body.getBoundingClientRect().top : 0;
}

This function will return the element's top position within the window or it will return 0 if you pass it something other than an element with the .getBoundingClientRect() method. This method has been around for a long time, so you shouldn't have to worry about your browser not supporting it.

Now, our element's top position is:

var element_top_position = getElementWindowTop(element);

And or element's bottom position is:

var element_bottom_position = element_top_position + element.clientHeight;

Now we can determine if the element is within the viewport by checking if the element's bottom position is lower than the viewport's top position and by checking if the element's top position is higher than the viewport's bottom position:

if(element_bottom_position >= window.scrollY 
&& element_top_position <= window_bottom_position){
    //element is in view
else
    //element is not in view

From there, you can perform the logic to add or remove an in-view class on your element, which you can then handle later with transition effects in your CSS.

I am absolutely amazed that I did not find this solution anywhere else, but I do believe that this is the cleanest and most effective solution, and it doesn't require you to load jQuery!

We can do something like this in modern browsers using ES6:

const isFullySeen = el => el &&
  typeof el.getBoundingClientRect === 'function' &&
  el.getBoundingClientRect()['bottom'] + window.scrollY <= 
    window.innerHeight + window.scrollY && 
  el.getBoundingClientRect()['top'] + window.scrollY <= 
    window.innerHeight + window.scrollY;

I added my code modification. Unfortunately, I can see everyone in their version and everyone omits the use of the debance function. Which answer is for your Event not to fire, for example, 200 times per second while scrolling.

$(window).scroll(function(){
        if (isInView($('.class'))){
            debounce(
                someFunction(), 5
            )
        }
    });
    function isInView(elem){
        if(document.documentElement.clientWidth > 991){
            return $(elem).offset().top - $(window).scrollTop() < $(elem).height();
        }else {
            doSometing;
        }
    }

On Typescript

  private readonly isElementInViewPort = (el: HTMLElement): boolean => {
      const rect = el.getBoundingClientRect();
      const elementTop = rect.top;
      const elementBottom = rect.bottom;
      const scrollPosition = el?.scrollTop || document.body.scrollTop;
      return (
        elementBottom >= 0 &&
        elementTop <= document.documentElement.clientHeight &&
        elementTop + rect.height > elementTop &&
        elementTop <= elementBottom &&
        elementTop >= scrollPosition
      );

};

The jquery scrollspy plugin will allow you to easily do this. https://github.com/thesmart/jquery-scrollspy

$('.tile').on('scrollSpy:enter', function() {
    console.log('enter:', $(this).attr('id'));
});

$('.tile').on('scrollSpy:exit', function() {
    console.log('exit:', $(this).attr('id'));
});

$('.tile').scrollSpy();

The only solution that worked for me is (return true when $("#elementToCheck") is visible):

$(document).scrollTop()+window.innerHeight+$("#elementToCheck").height()>$("#elementToCheck").offset().top

The other answers generally don't check if the element is in view along the X axis, i.e. could be in the current viewports Y range, but out of the X range. This function checks X and Y if any part of the item is showing in the viewport:

function checkElInView(el) {
    if (!el || !typeof el.getBoundingClientRect === "function") return false;
    const r = el.getBoundingClientRect();
    const vw = document.documentElement.clientWidth;
    const vh = document.documentElement.clientHeight;
    const inViewX = (r.left > 0 && r.left < vw) || (r.right < vw && r.right > 0);
    const inViewY = (r.top > 0 && r.top < vh) || (r.bottom < vh && r.bottom > 0);
    return inViewX && inViewY;
}