Vue: issue applying class when element is not in view - javascript

I want to apply a class to a DOM element only when this element is in view inside my viewport (any part of it appearing on screen), however my console log says it's always not in view so the css class is not being applied. For this purpose I'm using a vue directive and a scroll event listener, here is my directive:
Vue.directive('focus-toggle-class', {
isLiteral: true,
inserted: (el, binding, vnode) => {
let scrolled = false;
let rect = {};
let checkInView = function(){
if (inView) {
el.classList.add(binding.value);
console.log('in view');
}
else{
el.classList.remove(binding.value);
console.log('not in view');
}
};
window.addEventListener('load', function() {
rect = el.getBoundingClientRect();
console.log(rect);
checkInView();
window.addEventListener('scroll', function() {
scrolled = true;
});
});
let inView = (
rect.top >= 0 &&
rect.left >= 0 &&
rect.right <= (window.innerWidth || document.documentElement.clientWidth) &&
rect.bottom <= (window.innerHeight || document.documentElement.clientHeight)
)
let timeout = setInterval(function() {
if (scrolled) {
scrolled = false;
checkInView();
}
}, 2000);
}
});

Related

click on blank area and run function if element is visible

On click on the html body:
if element '#cap' is viewable, do something.
if element '#cap' is not viewable due to being scrolled past it, do something else.
I tried #Heretic Monkey's suggestion and moved the functions to the bottom of the js file but that didn't work at all.
As requested by the moderators I am stating that I tried #Heretic Monkey's suggestion and moved the functions to the bottom of the js file but that didn't work at all.
<thead id = 'cap'>
function isInViewport(el) {
rect = el.getBoundingClientRect();
return (rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight ||
document.documentElement.clientHeight) && rect.right <= (window.innerWidth ||
document.documentElement.clientWidth));
}
box = document.querySelector('#cap');
document.addEventListener('click', function() {
if (isInViewport(box)) {
alert('true');
} else {
alert('false');
}
});
Chrome console says: blank.js:3 Uncaught TypeError: Cannot read properties of null (reading 'getBoundingClientRect')
function isInViewport(el) {rect = el.getBoundingClientRect();
Can someone explain why this code does nothing except produce a console error?

You can use the IntersectionObserver which tells you if the element is in the view. You can use the target to determine where the click happened.
let isIntersecting;
var observer = new IntersectionObserver(onIntersection, {
root: null,
threshold: .5,
})
function onIntersection(entries, opts) {
isIntersecting = entries[0].isIntersecting;
}
observer.observe(document.querySelector('#thead'));
window.addEventListener("click", function (e) {
if (e.target.closest("table")) return;
console.log('Table not clicked and the header is', isIntersecting ? "visible" : "not visible");
});
table tr td {
border: 1px solid black;
}
<table>
<thead id="thead">
<tr>
<td>Header</td>
</tr>
</thead>
<tbody>
<tr><td>1</td></tr>
<tr><td>2</td></tr>
<tr><td>3</td></tr>
<tr><td>4</td></tr>
<tr><td>5</td></tr>
<tr><td>6</td></tr>
<tr><td>7</td></tr>
<tr><td>8</td></tr>
<tr><td>9</td></tr>
<tr><td>10</td></tr>
<tr><td>11</td></tr>
<tr><td>12</td></tr>
<tr><td>13</td></tr>
<tr><td>14</td></tr>
<tr><td>15</td></tr>
<tr><td>16</td></tr>
<tr><td>17</td></tr>
<tr><td>18</td></tr>
<tr><td>19</td></tr>
<tr><td>20</td></tr>
<tr><td>21</td></tr>
<tr><td>22</td></tr>
<tr><td>23</td></tr>
<tr><td>24</td></tr>
<tr><td>25</td></tr>
<tr><td>26</td></tr>
<tr><td>27</td></tr>
<tr><td>28</td></tr>
<tr><td>29</td></tr>
</tbody>
</table>

The element is not present in the DOM, check that the DOM is in a ready state before adding the click event:
function isInViewport(el) {
rect = el.getBoundingClientRect();
return (rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight ||
document.documentElement.clientHeight) && rect.right <= (window.innerWidth ||
document.documentElement.clientWidth));
}
document.addEventListener('DOMContentLoaded', function() {
document.addEventListener('click', function() {
box = document.querySelector('#cap');
if (isInViewport(box)) {
alert('true');
} else {
alert('false');
}
});
});
function isInViewport(el) {
rect = el.getBoundingClientRect();
return (rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight ||
document.documentElement.clientHeight) && rect.right <= (window.innerWidth ||
document.documentElement.clientWidth));
}
document.addEventListener('DOMContentLoaded', function() {
document.addEventListener('click', function() {
box = document.querySelector('#cap');
if (isInViewport(box)) {
alert('true');
} else {
alert('false');
}
});
});
<div id="cap"></div>

My original code was correct and sufficient. I simply created and targeted two large clickable divs with absolute position. Rather than listening for a body click.
<div id = 'left_div' onclick = 'ring ();'></div>
<div id = 'right_riv onclick = 'ring ();'></div>
function isInViewport(el) {
rect = el.getBoundingClientRect();
return (rect.top >= 0 && rect.left >= 0 && rect.bottom <= (window.innerHeight ||
document.documentElement.clientHeight) && rect.right <= (window.innerWidth ||
document.documentElement.clientWidth));
}
function ring() {
box = document.querySelector('#cap');
document.addEventListener('click', function() {
if (isInViewport(box)) {stone();} else {rock();}
});}

Start jQuery animation when content in visible viewport [duplicate]

I'm loading elements via AJAX. Some of them are only visible if you scroll down the page. Is there any way I can know if an element is now in the visible part of the page?

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');
}

This answer in Vanilla:
function isScrolledIntoView(el) {
var rect = el.getBoundingClientRect();
var elemTop = rect.top;
var elemBottom = rect.bottom;
// Only completely visible elements return true:
var isVisible = (elemTop >= 0) && (elemBottom <= window.innerHeight);
// Partially visible elements return true:
//isVisible = elemTop < window.innerHeight && elemBottom >= 0;
return isVisible;
}

Using IntersectionObserver API
(native in modern browsers)
It's easy & efficient to determine if an element is visible in the viewport, or in any scrollable container, by using an observer.
The need to attach a scroll event and manually checking on the event callback is eliminated, which is more efficient:
// define an observer instance
var observer = new IntersectionObserver(onIntersection, {
root: null, // default is the viewport
threshold: .5 // percentage of target's visible area. Triggers "onIntersection"
})
// callback is called on intersection change
function onIntersection(entries, opts){
entries.forEach(entry =>
entry.target.classList.toggle('visible', entry.isIntersecting)
)
}
// Use the observer to observe an element
observer.observe( document.querySelector('.box') )
// To stop observing:
// observer.unobserve(entry.target)
span{ position:fixed; top:0; left:0; }
.box{ width:100px; height:100px; background:red; margin:1000px; transition:.75s; }
.box.visible{ background:green; border-radius:50%; }
<span>Scroll both Vertically & Horizontally...</span>
<div class='box'></div>
Supported by modern browsers, including mobile browsers. Not supported in IE - View browsers support table

Update: use IntersectionObserver
The best method I have found so far is the jQuery appear plugin. Works like a charm.
Mimics a custom "appear" event, which fires when an element scrolls into view or otherwise becomes visible to the user.
$('#foo').appear(function() {
$(this).text('Hello world');
});
This plugin can be used to prevent unnecessary requests for content that's hidden or outside the viewable area.

Here's my pure JavaScript solution that works if it's hidden inside a scrollable container too.
Demo here (try resizing the window too)
var visibleY = function(el){
var rect = el.getBoundingClientRect(), top = rect.top, height = rect.height,
el = el.parentNode
// Check if bottom of the element is off the page
if (rect.bottom < 0) return false
// Check its within the document viewport
if (top > document.documentElement.clientHeight) return false
do {
rect = el.getBoundingClientRect()
if (top <= rect.bottom === false) return false
// Check if the element is out of view due to a container scrolling
if ((top + height) <= rect.top) return false
el = el.parentNode
} while (el != document.body)
return true
};
EDIT 2016-03-26: I've updated the solution to account for scrolling past the element so it's hidden above the top of the scroll-able container.
EDIT 2018-10-08: Updated to handle when scrolled out of view above the screen.

Plain vanilla to check if element (el) is visible in scrollable div (holder)
function isElementVisible (el, holder) {
holder = holder || document.body
const { top, bottom, height } = el.getBoundingClientRect()
const holderRect = holder.getBoundingClientRect()
return top <= holderRect.top
? holderRect.top - top <= height
: bottom - holderRect.bottom <= height
}
Usage with jQuery:
var el = $('tr:last').get(0);
var holder = $('table').get(0);
var isVisible = isElementVisible(el, holder);

jQuery Waypoints plugin goes very nice here.
$('.entry').waypoint(function() {
alert('You have scrolled to an entry.');
});
There are some examples on the site of the plugin.

How about
function isInView(elem){
return $(elem).offset().top - $(window).scrollTop() < $(elem).height() ;
}
After that you can trigger whatever you want once the element is in view like this
$(window).scroll(function(){
if (isInView($('.classOfDivToCheck')))
//fire whatever you what
dothis();
})
That works for me just fine

Tweeked Scott Dowding's cool function for my requirement-
this is used for finding if the element has just scrolled into the screen i.e it's top edge .
function isScrolledIntoView(elem)
{
var docViewTop = $(window).scrollTop();
var docViewBottom = docViewTop + $(window).height();
var elemTop = $(elem).offset().top;
return ((elemTop <= docViewBottom) && (elemTop >= docViewTop));
}

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();
});
};

Most answers here don't take into account that an element can also be hidden because it is scrolled out of view of a div, not only of the whole page.
To cover that possibility, you basically have to check if the element is positioned inside the bounds of each of its parents.
This solution does exactly that:
function(element, percentX, percentY){
var tolerance = 0.01; //needed because the rects returned by getBoundingClientRect provide the position up to 10 decimals
if(percentX == null){
percentX = 100;
}
if(percentY == null){
percentY = 100;
}
var elementRect = element.getBoundingClientRect();
var parentRects = [];
while(element.parentElement != null){
parentRects.push(element.parentElement.getBoundingClientRect());
element = element.parentElement;
}
var visibleInAllParents = parentRects.every(function(parentRect){
var visiblePixelX = Math.min(elementRect.right, parentRect.right) - Math.max(elementRect.left, parentRect.left);
var visiblePixelY = Math.min(elementRect.bottom, parentRect.bottom) - Math.max(elementRect.top, parentRect.top);
var visiblePercentageX = visiblePixelX / elementRect.width * 100;
var visiblePercentageY = visiblePixelY / elementRect.height * 100;
return visiblePercentageX + tolerance > percentX && visiblePercentageY + tolerance > percentY;
});
return visibleInAllParents;
};
It also lets you specify to what percentage it has to be visible in each direction.
It doesn't cover the possibility that it may be hidden due to other factors, like display: hidden.
This should work in all major browsers, since it only uses getBoundingClientRect. I personally tested it in Chrome and Internet Explorer 11.

isScrolledIntoView is a very needful function, so I tried it, it works for elements not heigher than the viewport, but if the element is bigger as the viewport it does not work. To fix this easily change the condition
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
to this:
return (docViewBottom >= elemTop && docViewTop <= elemBottom);
See demo here: http://jsfiddle.net/RRSmQ/

This considers any padding, border or margin the element has as well as elements larger than the viewport itself.
function inViewport($ele) {
var lBound = $(window).scrollTop(),
uBound = lBound + $(window).height(),
top = $ele.offset().top,
bottom = top + $ele.outerHeight(true);
return (top > lBound && top < uBound)
|| (bottom > lBound && bottom < uBound)
|| (lBound >= top && lBound <= bottom)
|| (uBound >= top && uBound <= bottom);
}
To call it use something like this:
var $myElement = $('#my-element'),
canUserSeeIt = inViewport($myElement);
console.log(canUserSeeIt); // true, if element is visible; false otherwise

Here is another solution:
<script type="text/javascript">
$.fn.is_on_screen = function(){
var win = $(window);
var viewport = {
top : win.scrollTop(),
left : win.scrollLeft()
};
viewport.right = viewport.left + win.width();
viewport.bottom = viewport.top + win.height();
var bounds = this.offset();
bounds.right = bounds.left + this.outerWidth();
bounds.bottom = bounds.top + this.outerHeight();
return (!(viewport.right < bounds.left || viewport.left > bounds.right || viewport.bottom < bounds.top || viewport.top > bounds.bottom));
};
if( $('.target').length > 0 ) { // if target element exists in DOM
if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
$('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info
} else {
$('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
}
}
$(window).on('scroll', function(){ // bind window scroll event
if( $('.target').length > 0 ) { // if target element exists in DOM
if( $('.target').is_on_screen() ) { // if target element is visible on screen after DOM loaded
$('.log').html('<div class="alert alert-success">target element is visible on screen</div>'); // log info
} else {
$('.log').html('<div class="alert">target element is not visible on screen</div>'); // log info
}
}
});
</script>
See it in JSFiddle

function isScrolledIntoView(elem) {
var docViewTop = $(window).scrollTop(),
docViewBottom = docViewTop + $(window).height(),
elemTop = $(elem).offset().top,
elemBottom = elemTop + $(elem).height();
//Is more than half of the element visible
return ((elemTop + ((elemBottom - elemTop)/2)) >= docViewTop && ((elemTop + ((elemBottom - elemTop)/2)) <= docViewBottom));
}

I needed to check visibility in elements inside scrollable DIV container
//p = DIV container scrollable
//e = element
function visible_in_container(p, e) {
var z = p.getBoundingClientRect();
var r = e.getBoundingClientRect();
// Check style visiblilty and off-limits
return e.style.opacity > 0 && e.style.display !== 'none' &&
e.style.visibility !== 'hidden' &&
!(r.top > z.bottom || r.bottom < z.top ||
r.left > z.right || r.right < z.left);
}

Building off of this great answer, you can simplify it a little further using ES2015+:
function isScrolledIntoView(el) {
const { top, bottom } = el.getBoundingClientRect()
return top >= 0 && bottom <= window.innerHeight
}
If you don't care about the top going out of the window and just care that the bottom has been viewed, this can be simplified to
function isSeen(el) {
return el.getBoundingClientRect().bottom <= window.innerHeight
}
or even the one-liner
const isSeen = el => el.getBoundingClientRect().bottom <= window.innerHeight

There is a plugin for jQuery called inview which adds a new "inview" event.
Here is some code for a jQuery plugin that doesn't use events:
$.extend($.expr[':'],{
inView: function(a) {
var st = (document.documentElement.scrollTop || document.body.scrollTop),
ot = $(a).offset().top,
wh = (window.innerHeight && window.innerHeight < $(window).height()) ? window.innerHeight : $(window).height();
return ot > st && ($(a).height() + ot) < (st + wh);
}
});
(function( $ ) {
$.fn.inView = function() {
var st = (document.documentElement.scrollTop || document.body.scrollTop),
ot = $(this).offset().top,
wh = (window.innerHeight && window.innerHeight < $(window).height()) ? window.innerHeight : $(window).height();
return ot > st && ($(this).height() + ot) < (st + wh);
};
})( jQuery );
I found this in a comment here ( http://remysharp.com/2009/01/26/element-in-view-event-plugin/ ) by a bloke called James

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.

I prefer using jQuery expr
jQuery.extend(jQuery.expr[':'], {
inview: function (elem) {
var t = $(elem);
var offset = t.offset();
var win = $(window);
var winST = win.scrollTop();
var elHeight = t.outerHeight(true);
if ( offset.top > winST - elHeight && offset.top < winST + elHeight + win.height()) {
return true;
}
return false;
}
});
so you can use it this way
$(".my-elem:inview"); //returns only element that is in view
$(".my-elem").is(":inview"); //check if element is in view
$(".my-elem:inview").length; //check how many elements are in view
You can easly add such code inside scroll event function etc. to check it everytime user will scroll the view.

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');
}
}

If you want to tweak this for scrolling item within another div,
function isScrolledIntoView (elem, divID)
{
var docViewTop = $('#' + divID).scrollTop();
var docViewBottom = docViewTop + $('#' + divID).height();
var elemTop = $(elem).offset().top;
var elemBottom = elemTop + $(elem).height();
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}

You can make use of jquery plugin "onScreen" to check if the element is in the current viewport when you scroll.
The plugin sets the ":onScreen" of the selector to true when the selector appears on the screen.
This is the link for the plugin which you can include in your project.
"http://benpickles.github.io/onScreen/jquery.onscreen.min.js"
You can try the below example which works for me.
$(document).scroll(function() {
if($("#div2").is(':onScreen')) {
console.log("Element appeared on Screen");
//do all your stuffs here when element is visible.
}
else {
console.log("Element not on Screen");
//do all your stuffs here when element is not visible.
}
});
HTML Code:
<div id="div1" style="width: 400px; height: 1000px; padding-top: 20px; position: relative; top: 45px"></div> <br>
<hr /> <br>
<div id="div2" style="width: 400px; height: 200px"></div>
CSS:
#div1 {
background-color: red;
}
#div2 {
background-color: green;
}

An example based off of this answer to check if an element is 75% visible (i.e. less than 25% of it is off of the screen).
function isScrolledIntoView(el) {
// check for 75% visible
var percentVisible = 0.75;
var elemTop = el.getBoundingClientRect().top;
var elemBottom = el.getBoundingClientRect().bottom;
var elemHeight = el.getBoundingClientRect().height;
var overhang = elemHeight * (1 - percentVisible);
var isVisible = (elemTop >= -overhang) && (elemBottom <= window.innerHeight + overhang);
return isVisible;
}

A more efficient version of this answer:
/**
* Is element within visible region of a scrollable container
* #param {HTMLElement} el - element to test
* #returns {boolean} true if within visible region, otherwise false
*/
function isScrolledIntoView(el) {
var rect = el.getBoundingClientRect();
return (rect.top >= 0) && (rect.bottom <= window.innerHeight);
}

Modified the accepted answer so that the element has to have it's display property set to something other than "none" to quality as visible.
function isScrolledIntoView(elem) {
var docViewTop = $(window).scrollTop();
var docViewBottom = docViewTop + $(window).height();
var elemTop = $(elem).offset().top;
var elemBottom = elemTop + $(elem).height();
var elemDisplayNotNone = $(elem).css("display") !== "none";
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop) && elemDisplayNotNone);
}

Here is a way to achieve the same thing using Mootools, in horizontal, vertical or both.
Element.implement({
inVerticalView: function (full) {
if (typeOf(full) === "null") {
full = true;
}
if (this.getStyle('display') === 'none') {
return false;
}
// Window Size and Scroll
var windowScroll = window.getScroll();
var windowSize = window.getSize();
// Element Size and Scroll
var elementPosition = this.getPosition();
var elementSize = this.getSize();
// Calculation Variables
var docViewTop = windowScroll.y;
var docViewBottom = docViewTop + windowSize.y;
var elemTop = elementPosition.y;
var elemBottom = elemTop + elementSize.y;
if (full) {
return ((elemBottom >= docViewTop) && (elemTop <= docViewBottom)
&& (elemBottom <= docViewBottom) && (elemTop >= docViewTop) );
} else {
return ((elemBottom <= docViewBottom) && (elemTop >= docViewTop));
}
},
inHorizontalView: function(full) {
if (typeOf(full) === "null") {
full = true;
}
if (this.getStyle('display') === 'none') {
return false;
}
// Window Size and Scroll
var windowScroll = window.getScroll();
var windowSize = window.getSize();
// Element Size and Scroll
var elementPosition = this.getPosition();
var elementSize = this.getSize();
// Calculation Variables
var docViewLeft = windowScroll.x;
var docViewRight = docViewLeft + windowSize.x;
var elemLeft = elementPosition.x;
var elemRight = elemLeft + elementSize.x;
if (full) {
return ((elemRight >= docViewLeft) && (elemLeft <= docViewRight)
&& (elemRight <= docViewRight) && (elemLeft >= docViewLeft) );
} else {
return ((elemRight <= docViewRight) && (elemLeft >= docViewLeft));
}
},
inView: function(full) {
return this.inHorizontalView(full) && this.inVerticalView(full);
}});

This method will return true if any part of the element is visible on the page. It worked better in my case and may help someone else.
function isOnScreen(element) {
var elementOffsetTop = element.offset().top;
var elementHeight = element.height();
var screenScrollTop = $(window).scrollTop();
var screenHeight = $(window).height();
var scrollIsAboveElement = elementOffsetTop + elementHeight - screenScrollTop >= 0;
var elementIsVisibleOnScreen = screenScrollTop + screenHeight - elementOffsetTop >= 0;
return scrollIsAboveElement && elementIsVisibleOnScreen;
}

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!

Lazy loading images on mobile

I'm using this lazy loading code.
JS CODE:
$(window).on('scroll touchmove', function(){
if( $('.touch').length) {
var images = $('.theme-slider img[data-lazy]');
images.each(function(index){
if(isElementVisible(this)) {
$(this).attr('src', $(this).attr('data-lazy'));
$(this).removeAttr('data-lazy');
}
})
if(images.length == 0) {
$(window).off('scroll touchmove');
}
}
});
// Checking if an image is within the viewport
function isElementVisible(el){
var rect = el.getBoundingClientRect();
return (
rect.top >= 0 &&
rect.left >= 0 &&
rect.bottom <= (window.innerHeight) &&
rect.right <= (window.innerWidth)
);
}
My problem is on iPhone when I'm scrolling horizontal if the image has entered the viewport it doesn't load, I have to scroll back and forward until it works.
Any ideas how I can solve it?

How to get the effect on navigation button

I am writing this code to change my navigation link colour(white to #03c1cb) based on the url address not but it doesn't run properly please help me. I want to change the color of navigation link at that particular url address
my html code is
<a href="#home" id="start1" class="scroll" style="text-decoration:none;position:absolute;
right:450px;top:37px;font-weight:bold;color:white;font-size:15px;z-index:200;
transition:0.5s" onmouseover="big(this)" onmouseout="small(this)">HOME</a>
function big(x) {
x.style.fontSize = "17px";
x.style.color = "#03c1cb";
}
function small(x) {
var y = location.hash;
if (x.href == y) {
x.style.fontSize = "17px";
x.style.color = "#03c1cb";
} else {
x.style.color = "white";
x.style.fontSize = "15px";
}
}
function isElementInViewport(el) {
//special bonus for those using jQuery
if (typeof jQuery === "function" && el instanceof jQuery) {
el = el[0];
}
var rect = el.getBoundingClientRect();
return (
rect.top >= 0 &&
rect.left >= 0 &&
rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /*or $j(window).height() */
rect.right <= (window.innerWidth || document.documentElement.clientWidth) /*or $j(window).width() */
);
}
// url change on clicking
$(document).ready(function() {
$(".scroll").click(function(e) {
e.preventDefault();
var section = this.href,
sectionClean = section.substring(section.indexOf("#"));
$("html, body").animate({
scrollTop: $j(sectionClean).offset().top
}, 1000, function() {
window.location.hash = sectionClean;
});
});
});
// listen for the scroll event
$(document).on("scroll", function() {
console.log("onscroll event fired...");
// check if the anchor elements are visible
$(".anchor").each(function(idx, el) {
if (isElementInViewport(el)) {
// update the URL hash
if (window.history.pushState) {
var urlHash = "#" + $j(el).attr("id");
window.history.pushState(null, null, urlHash);
}
}
});
});
Please help me

manipulate when inview.js is firing

i would like to know how i can manipulate the inview.js script that the moment when its fired is not at first pixels in viewport, and the last when the element is going out but rather for example 50pixels later or earlier.
the script of inview.js is
(function ($) {
function getViewportHeight() {
var height = window.innerHeight; // Safari, Opera
var mode = document.compatMode;
if ( (mode || !$.support.boxModel) ) { // IE, Gecko
height = (mode == 'CSS1Compat') ?
document.documentElement.clientHeight : // Standards
document.body.clientHeight; // Quirks
}
return height;
}
$(window).scroll(function () {
var vpH = getViewportHeight(),
scrolltop = (document.documentElement.scrollTop ?
document.documentElement.scrollTop :
document.body.scrollTop),
elems = [];
// naughty, but this is how it knows which elements to check for
$.each($.cache, function () {
if (this.events && this.events.inview) {
elems.push(this.handle.elem);
}
});
if (elems.length) {
$(elems).each(function () {
var $el = $(this),
top = $el.offset().top,
height = $el.height(),
inview = $el.data('inview') || false;
if (scrolltop > (top + height) || scrolltop + vpH < top) {
if (inview) {
$el.data('inview', false);
$el.trigger('inview', [ false ]);
}
} else if (scrolltop < (top + height)) {
if (!inview) {
$el.data('inview', true);
$el.trigger('inview', [ true ]);
}
}
});
}
});
// kick the event to pick up any elements already in view.
// note however, this only works if the plugin is included after the elements are bound to 'inview'
$(function () {
$(window).scroll();
});
})(jQuery);
all credits go to here
my attemp was to add a value to offset top top = $el.offset().top + 50, which works! but how can i change the value for the bottom up?
thanks ted

I'd recommend using http://imakewebthings.com/jquery-waypoints/
Which you can call like so to achieve your desired effect at 10% from the bottom:
$('.flyIn').waypoint(function() {
$(this).removeClass('hidden');
$(this).addClass('animated fadeInUp');
}, { offset: '90%' });

Categories