var id = document.querySelector("#arrowUp");
var arrowUp = window.pageYOffset >= 5;
console.log(arrowUp);
id.classList.toggle("arrowUp", arrowUp);
id.addEventListener('click', function() {
window.scrollTo(0, 0);
})
I am trying to insert a class in certain HTML based on the scroll, but the issue is this part of the code:
var arrowUp = window.pageYOffset >= 5;
It is not dynamically getting true or false based on the scroll and the condition window.pageYOffset >= 5; is not dynamically true or false right now. Hence anticipated class is not getting inserted/deleted.
How to bind this part of the code to scroll event
Add an EventListener for the scroll event.
var id = document.querySelector("#arrowUp");
id.addEventListener('click', function() {
window.scrollTo(0, 0);
})
window.addEventListener('scroll', function() {
var arrowUp = window.pageYOffset >= 5;
if (arrowUp == true) {
id.classList.add('visible');
} else {
id.classList.remove('visible');
}
})
You can't do this "dynamically", window.pageYOffset is not a magic dynamic variable, it's a getter (function without arguments that retrieves some value)
In order for this to work, you have to check on each scroll event is the condition holds true.
var id = document.querySelector("#arrowUp");
document.addEventListener("scroll", function() {
var arrowUp = window.pageYOffset >= 5;
console.log(arrowUp);
id.classList.toggle("arrowUp", arrowUp);
});
id.addEventListener('click', function() {
window.scrollTo(0, 0);
});
Related
This question already has an answer here:
jQuery trigger when 2/3s of div are in viewport
(1 answer)
Closed 6 years ago.
I would like to check if a class is added on an Element during the scroll and launch another function, just once, until the class is added to the next element.
here my first function :
function onScreen() {
$('article').each(function() {
var thisTop = $(this).offset().top - $(window).scrollTop();
var middleScreen = $(window).height() / 2;
if (thisTop < middleScreen && (thisTop + $(this).height()) > middleScreen) {
$(this).addClass('visible');
} else {
$(this).removeClass('visible');
}
});
}
// launch
$(window).on('load scroll', onScreen);
My seconde function : I would like to launch just once if the visible class is added to another article.
function textChange() {
var v = $('article.visible');
var el = $('.el', v);
var text = $(el).html();
$('.titre').html(text);
}
$(window).on('load scroll', textChange);
note : It's important to me to keep two separate function.
My issue is the scroll function get call textChange() each pixel I scroll on the page. Strangly, the onScreen() function add the visible class just once until the next article gonna be visible.
Thanks for yours suggestions.
Introduce a global variable that tells you if the function has been executed or not:
var textChanged = false;
In your textChange() function set it to true when the function was called the first time:
function textChange() {
if(!textChanged){
textChanged = true;
var v = $('article.visible');
var el = $('.el', v);
var text = $(el).html();
$('.titre').html(text);
}
}
EDIT: Alternatively you can do the check before the function gets called:
if (thisTop < middleScreen && (thisTop + $(this).height()) > middleScreen) {
$(this).addClass('visible');
if(!textChanged){
textChange();
}
} else {
$(this).removeClass('visible');
}
I was looking for a function that would scroll a given element into view with some smart behavior:
if an element is descendant of a scrollable element - that ancestor is scrolled rather than body.
if an element is descendant of a positioned element - body won't be scrolled.
I didn't find any suitable function, so I made one and wanted some expert opinion on it. Please check the plunkr http://plnkr.co/edit/DNGWLh5cH1Cr1coZbwpa?p=preview . There are problems with animated scroll in FF, so please use Chrome to check the logic.
To illustrate, what I'm looking for - here is the first update that came to mind - if we reached an element that can scroll, lets call it SC (Scroll Parent), we should not only scroll SC to make the target visible inside it, but also recursively scroll SC itself into view, since it may outside of the currently visible are of the page. Here is the update plunkr http://plnkr.co/edit/DNGWLh5cH1Cr1coZbwpa?p=preview (also applied fix for FF scrolling problem).
And here is the code of the function
function scrollTo(target){
//Position delta is used for scrollable elements other than BODY
var combinedPositionDelta = 0;
var previousParent = $(target);
var parent = $(target).parent();
while(parent){
combinedPositionDelta += previousParent.position().top - parent.position().top;
//If we reached body
if(parent.prop("tagName").toUpperCase() == "BODY"){
scrollBody(target.offset().top);
break;
}
//if we reached an element that can scroll
if(parent[0].scrollHeight > parent.outerHeight()){
scrollElementByDelta(parent,combinedPositionDelta);
//Recursively scroll parent into view, since it itself might not be visible
scrollTo(parent);
break;
}
//if we reached a apositioned element - break
if(parent.css('position').toUpperCase() != 'STATIC'){
console.log("Stopping due to positioned parent " + parent[0].outerHTML);
break;
}
previousParent = parent;
parent = parent.parent();
}
}
var offsetSkin = 20;
function scrollElementByDelta(element,offsetDelta){
$(element).animate({
scrollTop: element.scrollTop() + (offsetDelta - offsetSkin)
}, 1000);
}
function scrollBody(offset){
$('body,html').animate({
scrollTop: offset - offsetSkin
}, 1000);
}
Well I'm Using this one which works very well for me:
function scrollIntoView (element, alignTop) {
var document = element.ownerDocument;
var origin = element, originRect = origin.getBoundingClientRect();
var hasScroll = false;
var documentScroll = this.getDocumentScrollElement(document);
while (element) {
if (element == document.body) {
element = documentScroll;
} else {
element = element.parentNode;
}
if (element) {
var hasScrollbar = (!element.clientHeight) ? false : element.scrollHeight > element.clientHeight;
if (!hasScrollbar) {
if (element == documentScroll) {
element = null;
}
continue;
}
var rects;
if (element == documentScroll) {
rects = {
left : 0,
top : 0
};
} else {
rects = element.getBoundingClientRect();
}
// check that elementRect is in rects
var deltaLeft = originRect.left - (rects.left + (parseInt(element.style.borderLeftWidth, 10) | 0));
var deltaRight = originRect.right
- (rects.left + element.clientWidth + (parseInt(element.style.borderLeftWidth, 10) | 0));
var deltaTop = originRect.top - (rects.top + (parseInt(element.style.borderTopWidth, 10) | 0));
var deltaBottom = originRect.bottom
- (rects.top + element.clientHeight + (parseInt(element.style.borderTopWidth, 10) | 0));
// adjust display depending on deltas
if (deltaLeft < 0) {
element.scrollLeft += deltaLeft;
} else if (deltaRight > 0) {
element.scrollLeft += deltaRight;
}
if (alignTop === true && !hasScroll) {
element.scrollTop += deltaTop;
} else if (alignTop === false && !hasScroll) {
element.scrollTop += deltaBottom;
} else {
if (deltaTop < 0) {
element.scrollTop += deltaTop;
} else if (deltaBottom > 0) {
element.scrollTop += deltaBottom;
}
}
if (element == documentScroll) {
element = null;
} else {
// readjust element position after scrolls, and check if vertical scroll has changed.
// this is required to perform only one alignment
var nextRect = origin.getBoundingClientRect();
if (nextRect.top != originRect.top) {
hasScroll = true;
}
originRect = nextRect;
}
}
}
}
I hope this helps.
If you do not mind venturing into jQuery, the scrollTo plugin is the best bet. It handles most needs and gives a very refined smooth trasition.
Hope it helps.
I have a "follow scroll" function, but I want it to turn off when it returns to a certain point. My code is as follows:
scrollSidebar: function(scroll) {
var elemPos = $('#bestvideos-2').offset().top,
scroll2 = scroll;
if(scroll2 >= elemPos) {
$('#bestvideos-2').animate({
'margin-top':(scroll - 315)+'px'
},0);
} else {
$('#bestvideos-2').css('margin-top','0');
}
}
$(window).scroll(function() {
var scrollHeight = $(window).scrollTop();
Scroll.scrollSidebar(scrollHeight);
})
The problem is - every time I get up, it goes way up, not following scroll. What I'm thinking is storing a variable elemPos somewhere and keep it static (now it's changing each time I scroll).
What can I do with this?
Pass the value to the scrollSidebar function - make sure that the var elemPos = $('#bestvideos-2').offset().top is executed on dom ready
scrollSidebar: function (elemPos, scroll) {
var scroll2 = scroll;
if (scroll2 >= elemPos) {
$('#bestvideos-2').animate({
'margin-top': (scroll - 315) + 'px'
}, 0);
} else {
$('#bestvideos-2').css('margin-top', '0');
}
}
var elemPos = $('#bestvideos-2').offset().top
$(window).scroll(function () {
var scrollHeight = $(window).scrollTop();
Scroll.scrollSidebar(elemPos, scrollHeight);
})
I need a bit of advice as I can't get my noob head around the following, please see this fiddle: http://jsfiddle.net/NtUpw/
The code works as intended, but when the current div offset goes > 41 and prev is hit, I'd like the page to return to the beginning of the current div, not to one before that. Any idea how can I add this condition?
I realise the current code isn't the cleanest (actually it's a combination of two fiddles), but I hope someone could take a look at it anyway. Thanks.
$('a.buttons').on('click', function (e) {
e.preventDefault();
var t = $(this).text(),
that = $(this);
if (t === 'next' && $('.current').next('div.post').length > 0 ) {
var $next = $('.current').next('.post');
var top = $next.offset().top;
$('body').animate({
scrollTop: $('.current').next('div.post').offset().top - 40
});
} else if (t === 'prev' && $('.current').prev('div.post').length > 0 ) {
var $prev = $('.current').prev('.post');
var top = $prev.offset().top;
$('body').animate({
scrollTop: $('.current').prev('div.post').offset().top - 40
});
}
$(window).bind('scroll', function () {
$('.post').each(function () {
var post = $(this);
var position = post.position().top - $(window).scrollTop();
if (position <= 40) {
post.addClass('current');
post.prev().removeClass("current");
} else {
post.removeClass('current');
}
});
});
The prev action works by moving always the div to the previous; the solution is to check the current position of the navigator respect to the current div:
var $prev;
var top;
var firstElem = true;
if ($('.current').prev('div.post').length > 0) {
$prev = $('.current').prev('.post');
top = $prev.offset().top;
firstElem = false
}
var currTop = $('.current').offset().top;
var navBottom = $('.navigation').offset().top + 40;
if (currTop == navBottom && !firstElem) {
$('body,html').animate({
scrollTop: $('.current').prev('div.post').offset().top - 40
});
with this the navigator jumps to the previous div only if is not at the top of the current; alternatively jumps to the previous.
The firefox issue depends on how Firefox places the overflow, it places it at the html level not at body like other browsers.
To let it work you must define the scrolling action with:
$('body,html').animate({
});
Working fiddle: http://jsfiddle.net/IrvinDominin/2QYgR/3/
i have 3 divs with scrollbars.
If i scroll in div 1 i want to scroll div 2 and 3 in the opposite direction.
The distance scrolled should be half the distance of div 1.
This is what i have now (small part, rest is in jsfiddle), which works for 1 div.
$("#textBox1").scroll(function () {
console.log("scroll 1");
var offset = $("#textBox1").scrollTop() - scrollPosTBox1;
var half_offset = offset/2.0;
disable1 = true;
if(disable2 == false) {
$("#textBox2").scrollTop(scrollPosTBox2 - half_offset);
}
if(disable3 == false) {
$("#textBox3").scrollTop(scrollPosTBox3 - half_offset);
}
disable1 = false;
});
However, if i try to get the same for the other 2 divs then i can't scroll anything anymore.
This is because div 1 triggers div 2 and div 2 triggers back to div 1 for example.
I tried to fix this with the disable code but it doesn't help.
Can someone help me?
http://jsfiddle.net/XmYh5/1/
No disrespect to #EmreErkan and #Simon for their effort. Here's a no-click version of this.
var $boxes = $("#textBox1,#textBox2,#textBox3"),
active;
$boxes.scrollTop(150);
// set initial scrollTop values
updateScrollPos();
// bind mouseenter:
// 1) find which panel is active
// 2) update scrollTop values
$boxes.mouseenter(function () {
active = this.id;
updateScrollPos();
});
// bind scroll for all boxes
$boxes.scroll(function (e) {
$this = $(this);
// check to see if we are dealing with the active box
// if true then set scrolltop of other boxes relative to the active box
if(this.id == active){
var $others = $boxes.not($this),
offset = $this.scrollTop()-$this.data("scroll"),
half_offset = offset / 2;
$others.each(function(){
$this = $(this);
$this.scrollTop($this.data("scroll") - half_offset);
});
}
});
// utility function:
// assign scrollTop values element's data attributes (data-scroll)
function updateScrollPos() {
$boxes.each(function(){
$this = $(this);
$this.data("scroll",$this.scrollTop());
});
}
Fiddle
You can use a variable to determine active textbox with .mousedown() and do the trick if it's active;
var activeScroll = '';
$("#textBox1").on('mousedown focus mouseenter', function () {
activeScroll = 'scroll1';
}).scroll(function () {
if (activeScroll == 'scroll1') {
console.log("scroll 1");
var offset = $("#textBox1").scrollTop() - scrollPosTBox1;
var half_offset = offset / 2.0;
$("#textBox2").scrollTop(scrollPosTBox2 - half_offset);
$("#textBox3").scrollTop(scrollPosTBox3 - half_offset);
}
});
You can check your updated jsFiddle here.
Finally got a dynamic solution for this, was more complex than I thought but I think I got it:
http://jsfiddle.net/XmYh5/14/
var initialTop = 150,
factor = 2;
$(".textBox")
.addClass('disabled')
.scrollTop(initialTop)
.on('scroll', function () {
var $this = $(this);
if(!$this.is('.disabled')) {
this.lastOffset = this.lastOffset || initialTop;
var offset = $this.scrollTop(),
step = (offset - this.lastOffset) / factor;
$this.siblings().each( function() {
var $this = $(this),
offset = $this.scrollTop() - step;
$this.scrollTop(offset);
this.lastOffset = offset;
});
this.lastOffset = offset;
}
})
.on('mouseenter', function() {
$(this).removeClass('disabled').siblings().addClass('disabled');
});