Develop Reference

About "paragraph sliding" in html

I want to achieve such a function as paragraph sliding (I don't know how to explain paragraph sliding)
So I just put it on the website for you to see
(It may take a while to enter)
https://grayraven.tw/
Like this one after another
I tried to write it myself, but there was no response after I wrote it
Below is my code
var mousewheel = (/Firefox/i.test(navigator.userAgent)) ?
"DOMMouseScroll" : "mousewheel";
var IDK = 1
slide.addEventListener(mousewheel,
function (e) {
if (e.wheelDelta > 0 || e.detail < 0) {
IDK + 1
$("html,body").animate({scrollTop: $("#" + IDK ).offset().top}, 1000);
} else {
if(IDK=1){
console.log("NO")
}else{
IDK - 1
$("html,body").animate({scrollTop: $("#" + IDK ).offset().top}, 1000);
}
}
}, false);
If you can tell me how to write, thank you very much
My English is not very good, please forgive me

Did you mean this?
//Set each section's height equals to the window height
$('section').height($(window).height());
/*set the class 'active' to the first element
this will serve as our indicator*/
$('section').first().addClass('active');
/* handle the mousewheel event together with
DOMMouseScroll to work on cross browser */
$(document).on('mousewheel DOMMouseScroll', function (e) {
e.preventDefault();//prevent the default mousewheel scrolling
var active = $('section.active');
//get the delta to determine the mousewheel scrol UP and DOWN
var delta = e.originalEvent.detail < 0 || e.originalEvent.wheelDelta > 0 ? 1 : -1;
//if the delta value is negative, the user is scrolling down
if (delta < 0) {
//mousewheel down handler
next = active.next();
//check if the next section exist and animate the anchoring
if (next.length) {
/*setTimeout is here to prevent the scrolling animation
to jump to the topmost or bottom when
the user scrolled very fast.*/
var timer = setTimeout(function () {
/* animate the scrollTop by passing
the elements offset top value */
$('body, html').animate({
scrollTop: next.offset().top
}, 'slow');
// move the indicator 'active' class
next.addClass('active')
.siblings().removeClass('active');
clearTimeout(timer);
}, 800);
}
} else {
//mousewheel up handler
/*similar logic to the mousewheel down handler
except that we are animate the anchoring
to the previous sibling element*/
prev = active.prev();
if (prev.length) {
var timer = setTimeout(function () {
$('body, html').animate({
scrollTop: prev.offset().top
}, 'slow');
prev.addClass('active')
.siblings().removeClass('active');
clearTimeout(timer);
}, 800);
}
}
});
body, html {
margin:0;
padding:0;
overflow:hidden;
}
section {
height:100vh!important;
font-size:30px;
display:flex;
justify-content:center;
align-items:center;
color:white;
}
.bg1{background-color:#FAAD80;}
.bg2{background-color:#FF6767;}
.bg3{background-color:#FF3D68;}
.bg4{background-color:#A73489;}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<section class="bg1">First</section>
<section class="bg2">Second</section>
<section class="bg3">Third</section>
<section class="bg4">Fourth</section>

How to listen to only the first scroll event on javascript/jquery?

I'm currently working on implementing my own version of snap-scrolling using vanilla JavaScript, and while I've got it mostly working as of now, I'm having trouble handling the scroll events.
My HTML looks something like this:
<div class="container">
<div id="item1"></div>
<div id="item2"></div>
<div id="item3"></div>
<div id="item4"></div>
</div>
And my JS looks something like this:
var pos = 0;
var isScrolling = false;
var id = 1;
$(window).scroll(function() {
if (!isScrolling) {
isScrolling = true;
var curPos = $(this).scrollTop();
if (curPos > pos) {
// scrolling down
if (id < 4) {
id++;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500);
}
} else {
// scrolling up
if (id > 1) {
id--;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500);
}
}
isScrolling = false;
pos = curPos;
}
});
What currently happens is when I scroll down my mouse wheel, it will do the animation but will keep proceeding to the next divs because of the multiple scroll events being fired. How do I make it so that it only listens to the first event (whether it scrolls up or down)?

A hacky way is to use timer:
var pos = 0;
var isScrolling = false;
var id = 1;
var lastScrollTime = $.now();
$(window).scroll(function() {
if ((!isScrolling)&&((($.now()-lastScrollTime)>3000)) {
isScrolling = true;
var curPos = $(this).scrollTop();
if (curPos > pos) {
// scrolling down
if (id < 4) {
id++;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500);
}
} else {
// scrolling up
if (id > 1) {
id--;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500);
}
}
isScrolling = false;
pos = curPos;
lastScrollTime = $.now();
}
});

You can register one time listeners in jQuery using jQuery.one.
EDIT:
You can use the complete callback of jQuery.animate to stop/start responding to scroll events.
var isScrolling = false;
$(window).on('scroll', function () {
if (!isScrolling) {
isScrolling = true;
var curPos = $(this).scrollTop();
if (curPos > pos) {
// scrolling down
if (id < 4) {
id++;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500,function(){
isScrolling = false;
});
}
} else {
// scrolling up
if (id > 1) {
id--;
$('html, body').animate({
scrollTop: $('#item' + id).offset().top
}, 500,function(){
isScrolling = false;
});
}
}
pos = curPos;
}
});

There's no easy way to deal with what it is known as kinetic scrolling.
Browsers do not provide developers a proper way to distinguish the meaningful scrolling from the inertial ones.
However, there are some attempts out there that aims to solve this issue, such as Lethargy.
Not 100% ideal, but very close to it.
Other than that, you can take a look at libraries like fullPage.js where another attempt to solve the issue was made.

jQuery scrollTop() returns wrong offset on scroll-direction change

I'm trying to get the correct scroll direction via jQuery's "scroll" event.
For this, I'm using the solution here: https://stackoverflow.com/a/4326907/8407840
However, if I change the direction of my scroll, the offset returned by scrollTop is incorrect on the first time. This results in the following behavior:
Wheel down -> down
Wheel down -> down
Wheel up -> down
Wheel up -> up
Wheel down -> up
Wheel down -> down
... and so on, I think you get it.
var ACTIVE_SECTION = null;
var ANIMATION_DURATION = 700;
$(document).ready(function() {
ACTIVE_SECTION = $("section:first-of-type").get(0);
var prevPosition = $(window).scrollTop();
$(window).on("scroll", function() {
doScrollingStuff(prevPosition);
});
});
function doScrollingStuff(prevPosition) {
var ctPosition = $(window).scrollTop();
var nextSection = ACTIVE_SECTION;
// Remove and re-append event, to prevent it from firing too often.
$(window).off("scroll");
setTimeout(function() {
$(window).on("scroll", function() {
doScrollingStuff(prevPosition);
});
}, ANIMATION_DURATION + 100);
// Determine scroll direction and target the next section
if(ctPosition < prevPosition) {
console.log("up");
nextSection = $(ACTIVE_SECTION).prev("section").get(0);
} else if(ctPosition > prevPosition) {
console.log("down");
nextSection = $(ACTIVE_SECTION).next("section").get(0);
}
// If a next section exists: Scroll to it!
if(typeof nextSection != 'undefined') {
var offset = $(nextSection).offset();
$("body, html").animate({
scrollTop: offset.top
}, ANIMATION_DURATION);
ACTIVE_SECTION = nextSection;
} else {
nextSection = ACTIVE_SECTION;
}
console.log(ACTIVE_SECTION);
prevPosition = ctPosition;
}
section {
width:100%;
height:100vh;
padding:60px;
box-sizing:border-box;
}
section:nth-child(1) { background:#13F399; }
section:nth-child(2) { background:#14FD43; }
section:nth-child(3) { background:#4EE61E; }
section:nth-child(4) { background:#BEFD14; }
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<section id="sect1">Section 1</section>
<section id="sect2">Section 2</section>
<section id="sect3">Section 3</section>
<section id="sect4">Section 4</section>
Here's a pen, where you can see my implementation: https://codepen.io/EigenDerArtige/pen/aVEyxd
I am trying to accomplish an autoscroll to the next or previous section, whenever the user scrolls or swipes up/down... Therefore I only fire the "scroll"-event once every second, to prevent multiple scrolljacks all happening at once... However the above behavior seems to result in the user being scrolled to the wrong section.
I've been trying for a couple of hours now to get it working, but to no avail. Help is greatly appreciated!

The problem lies in the assignment prevPosition = ctPosition.
Each time the scroll handler runs, var ctPosition = $(window).scrollTop(); is good for determining scroll direction, however it's not the value that should be rememberad as prevPosition.
prevPosition needs to be $(window).scrollTop() as measured after the animation has completed.
Try this :
$(document).ready(function() {
var ANIMATION_DURATION = 700;
var ACTIVE_SECTION = $("section:first-of-type").eq(0);
var prevPosition = $(window).scrollTop();
$(window).on("scroll", doScrollingStuff);
function doScrollingStuff(e) {
$(window).off("scroll");
var ctPosition = $(window).scrollTop();
var nextSection = (ctPosition < prevPosition) ? ACTIVE_SECTION.prev("section") : (ctPosition > prevPosition) ? ACTIVE_SECTION.next("section") : ACTIVE_SECTION; // Determine scroll direction and target the next section
// If next section exists and is not current section: Scroll to it!
if(nextSection.length > 0 && nextSection !== ACTIVE_SECTION) {
$("body, html").animate({
'scrollTop': nextSection.offset().top
}, ANIMATION_DURATION).promise().then(function() {
// when animation is complete
prevPosition = $(window).scrollTop(); // remember remeasured .scrollTop()
ACTIVE_SECTION = nextSection; // remember active section
$(window).on("scroll", doScrollingStuff); // no need for additional delay after animation
});
} else {
setTimeout(function() {
$(window).on("scroll", doScrollingStuff);
}, 100); // Debounce
}
}
});

javascript - Need onclick to go full distance before click works again

I have this javascript function I use that when clicked goes a certain distance. This is used within a scroller going left to right that uses about 7 divs. My question is how do I get the click to go the full distance first before the click can be used again? The issue is if the user rapidly clicks on the arrow button it resets the distance and sometimes can end up in the middle of an image instead of right at the seam. What code am I missing to accomplish this?
$(function () {
$("#right, #left").click(function () {
var dir = this.id == "right" ? '+=' : '-=';
$(".outerwrapper").stop().animate({ scrollLeft: dir + '251' }, 1000);
});
});

I would've thought that the easiest way would be to have a boolean flag indicating whether or not the animation is taking place:
$(function () {
var animating = false,
outerwrap = $(".outerwrapper");
$("#right, #left").click(function () {
if (animating) {return;}
var dir = (this.id === "right") ? '+=' : '-=';
animating = true;
outerwrap.animate({
scrollLeft: dir + '251'
}, 1000, function () {
animating = false;
});
});
});
works for me: http://jsfiddle.net/BYossarian/vDtwy/4/

Use .off() to unbind the click as soon as it occurs, then re-bind it once the animation completes.
function go(elem){
$(elem).off('click'); console.log(elem);
var dir = elem.id == "right" ? '+=' : '-=';
$(".outerwrapper").stop().animate({ left: dir + '251' }, 3000, function(){
$("#right, #left").click(go);
});
}
$("#right, #left").click(function () {
go(this);
});
jsFiddle example
You can see in this simplified example that the click event is unbound immediately after clicking, and then rebound once the animation completes.

Use an automatic then call like this
var isMoving = false;
$(function () {
$("#right, #left").click(function () {
if (isMoving) return;
isMoving = true;
var dir = this.id == "right" ? '+=' : '-=';
$(".outerwrapper").stop().animate({ scrollLeft: dir + '251' }, 1000).then(function(){isMoving = false}());
});
});

I think that you miss the fact that when you make stop() you actually position the slider at some specific point. I.e. if your scroller is 1000px and you click left twice very quickly you will probably get
scrollLeft: 0 - 251
scrollLeft: -2 - 251
So, I think that you should use an index and not exactly these += and -= calculations. For example:
$(function () {
var numberOfDivs = 7;
var divWidth = 251;
var currentIndex = 0;
$("#right, #left").click(function () {
currentIndex = this.id == "right" ? currentIndex+1 : currentIndex-1;
currentIndex = currentIndex < 0 ? 0 : currentIndex;
currentIndex = currentIndex > numberOfDivs ? numberOfDivs : currentIndex;
$(".outerwrapper").stop().animate({ scrollLeft: (currentIndex * divWidth) + "px" }, 1000);
});
});
A big benefit of this approach is that you are not disabling the clicking. You may click as many times as you want and you can do that quickly. The script will still works.

This will work perfectly fine:
var userDisplaysPageCounter = 1;
$('#inventory_userdisplays_forward_button').bind('click.rightarrowiventory', function(event) {
_goForwardInInventory();
});
$('#inventory_userdisplays_back_button').bind('click.leftarrowiventory', function(event) {
_goBackInInventory();
});
function _goForwardInInventory()
{
//$('#inventory_userdisplays_forward_button').unbind('click.rightarrowiventory');
var totalPages = $('#userfooterdisplays_list_pagination_container div').length;
totalPages = Math.ceil(totalPages/4);
// alert(totalPages);
if(userDisplaysPageCounter < totalPages)
{
userDisplaysPageCounter++;
$( "#userfooterdisplays_list_pagination_container" ).animate({
left: "-=600",
}, 500, function() {
});
}
}
function _goBackInInventory()
{
//$('#inventory_userdisplays_back_button').unbind('click.leftarrowiventory');
if(userDisplaysPageCounter > 1)
{
userDisplaysPageCounter--;
$( "#userfooterdisplays_list_pagination_container" ).animate({
left: "+=600",
}, 500, function() {
});
}
}

I second BYossarian's answer.
Here is a variation on his demo, which "skips" the animation when the user clicks several times quickly on the buttons :
$(function () {
var targetScroll = 0,
outerwrap = $(".outerwrapper");
$("#right, #left").click(function () {
// stop the animation,
outerwrap.stop();
// hard set scrollLeft to its target position
outerwrap.scrollLeft(targetScroll*251);
if (this.id === "right"){
if (targetScroll < 6) targetScroll += 1;
dir = '+=251';
} else {
if (targetScroll > 0) targetScroll -=1;
dir = '-=251';
}
outerwrap.animate({ scrollLeft: dir }, 1000);
});
});
fiddle

Javascript Scroll up and Down buttons

Im trying to make 2 buttons, one called "up" and one called "down".
Those should when I hold down my mouse on one of them, it should scroll up or down the whole page.
I tried with this code, but it didn't worked well.
Up
down​
<script>
$(document).ready(function() {
$("#down").hover(function () {
scroll_page("down");
}, function() { $('.content').stop(); });
$("#up").hover(function () {
scroll_page("up");
}, function() { $('.content').stop(); });
});
function scroll_page(direction) {
var scrolled = $(window).scrollTop();
if (direction == 'up') {
var scroll = scrolled + 100;
}else{
var scroll = scrolled - 100;
}
$("html, body").animate({ scrollTop: scroll }, "fast");
}
​
</script>
Does anyone have any ideas what to do?