Develop Reference

Animate an element in Javascript on mousemove

I have two DIV's of different widths on top of each other. The top DIV displayDIV is wider than the bottom DIV captureDIV.
In the displayDIV I'm drawing a dot who's X position is proportionate to the mouse position within captureDIV.
As you move the mouse in captureDIV the dot moves proportionately in DisplayDIV.
It makes much more sense if you look at this fiddle
My code is as follows...
let capture = document.getElementById('captureDIV');
let display = document.getElementById('displayDIV');
let circle = document.getElementById('circle');
capture.addEventListener('mousemove', handleMouseMove);
function handleMouseMove(event) {
const captureRect = capture.getBoundingClientRect();
const captureWidth = captureRect.right - captureRect.left;
const relativeX = event.x - captureRect.left;
let percent = (relativeX / captureWidth) * 100;
let roundedPercent = parseFloat(Math.round(percent * 100) / 100).toFixed(2);
moveDotTo(roundedPercent);
}
function moveDotTo(percentage) {
const displayRect = display.getBoundingClientRect();
const displayWidth = displayRect.right - displayRect.left;
const circleX = displayRect.left + displayWidth * (percentage / 100);
const circleY = displayRect.top + (displayRect.height / 2);
const style = `top:${circleY}px;left:${circleX}px;`;
circle.setAttribute('style', style);
}
I also have a number of buttons that can set the position of the dot within DisplayDIV such as...
let move20 = document.getElementById('move20');
move20.addEventListener('click', function(event) {
moveDotTo(20);
});
Using Vanilla JS not CSS tricks, how can I create a function to animate (rather than move) the dot from its existing position to the new position.
function animateDotTo(percentage) {
// clever code here
}
I need to be able to call the animateDotTo(percentage) function from either a button or from the mousemove event handler.
The dot should always animate to its new position regardless of how the move is triggered. For instance if the mouse is moved out of the left side of the captureDIV round the bottom and then into the right side of the captureDIV the dot should animate across the DisplayDIV not jump as it does now. Equally pressing one of the move to x% buttons should animate the dot from its current position to the new one.

If you are drawing a circle and moving it around, I would suggest drawing to a <canvas> element instead of moving a <div> by setting its top and left properties. Even using transform: translate(x, y) might be better.
In order to smoothly transition your dot from one location to another, using JavaScript, you will want:
The dot's current position as x and y coordinates,
The dot's target position as x and y coordinates, and
The speed at which the dot moves as a scalar.
Updating the current position is done at every animation frame with window.requestAnimationFrame. With these in hand, and a way of applying the resulting calculated position to the dot, you can use a method like this one: How to move an object using X and Y coordinates in JavaScript to move your dot (the example moves a canvas, but if you know the x and y, then you can set them to top and bottom).

Answering my own question, with thanks to Billy Brown for pointing me in the right direction. Using window.requestAnimationFrame is the way to go.
var currentPercentage;
var startPercentage;
var targetPercentage;
function animateDotTo(percentage) {
targetPercentage = percentage;
startPercentage = currentPercentage;
window.requestAnimationFrame(step);
}
function step(timestamp) {
var fps = 7;
var maxStep = 30;
var distStartToTarget = Math.abs(startPercentage - targetPercentage);
var stepSize = Math.min(distStartToTarget / fps, maxStep);
if (targetPercentage < startPercentage) {
currentPercentage -= stepSize,0;
if (currentPercentage > targetPercentage) {
window.requestAnimationFrame(step);
}
} else if (targetPercentage > startPercentage) {
currentPercentage += stepSize,100;
if (currentPercentage < targetPercentage) {
window.requestAnimationFrame(step);
}
} else {
return;
}
if (currentPercentage > 100 ) { currentPercentage = 100; }
if (currentPercentage < 0 ) { currentPercentage = 0; }
moveDotTo(currentPercentage);
}
Updated fiddle

A simple trick in css transition will fix this.
Of course. You don't want it to animate when you're actually moving the mouse. So what I did is that I separate the transition css property on another class and then remove that class on mouse move, re-attaching it when we click the move buttons.
CSS
#circle {
position: absolute;
left: -100px;
top: -100px;
width: 10px;
height: 10px;
border-radius: 50%;
background-color: #000;
transition: none;
}
#circle.animate{
transition: 500ms ease;
}
JS
move20.addEventListener('click', function(event) {
moveDotTo(20); animateDotTo();
});
move60.addEventListener('click', function(event) {
moveDotTo(60);animateDotTo();
});
move80.addEventListener('click', function(event) {
moveDotTo(80);animateDotTo();
});
function moveDotTo(percentage) {
circle.classList.remove("animate");
const displayRect = display.getBoundingClientRect();
const displayWidth = displayRect.right - displayRect.left;
const circleX = displayRect.left + displayWidth * (percentage / 100);
const circleY = displayRect.top + (displayRect.height / 2);
const style = `top:${circleY}px;left:${circleX}px;`;
circle.setAttribute('style', style);
}
function animateDotTo(percentage) {
circle.classList.add("animate");
}
http://jsfiddle.net/8pm2grjd/
If you want it to animate even if you're triggering the movement using mousemove, you can disregard the class approach and just slap the transition property on the css. But this will simulate the annoying mouse delay effect similar to input delay on video games due to V-Sync.

Java Script scroll top with transition duration

this is my function. i cant find how to add transition duration in it. it just takes me straight upto top. syntax is what i'm looking for. idk much about js.
function topFunction() {
document.body.scrollTop=0 ;
document.documentElement.scrollTop =0 ;
}

Try using this in place of your function:
window.scrollTo({
top: 100,
left: 100,
behavior: 'smooth'
});
Reference

You can add transition duration by using below code.
function topFunction() {
currentYOffset = self.pageYOffset;
initYOffset = currentYOffset;
var intervalId = setInterval(function(){
currentYOffset -= initYOffset*0.05;
document.body.scrollTop = currentYOffset ;
document.documentElement.scrollTop = currentYOffset;
if(self.pageYOffset == 0){
clearInterval(intervalId);
}
}, 20);
}
You can set smoothness of the transition by editing the value of interval. I have set it as 20.

Here is a jQuery solution, using the jQuery.animate function.
The function gives you the ability to change the animation time, as well as the selector on which the animation is being applied, so that you can scroll other elements, too.
/**
* Scroll to a given point on the page with animation
*
* #param {int} scrollValue - The top position to scroll to
* #param {int} [animationTime] - Speed of the animation (in milliseconds)
* #param {string} [selector] - Which element to scroll. By default, it is the html/body
*/
function animateScrollTo(scrollValue, animationTime, selector){
if(typeof animationTime === "undefined"){
animationTime = 520;
}
if(typeof selector === "undefined"){
selector = "html, body";
}
jQuery(selector).animate({scrollTop: scrollValue}, animationTime);
}

body {
scroll-behavior: smooth;
}
Just use this property and document.getElementById('some-id').scrollTop = 0 will work with smooth transition/animation.

JS for smooth scroll to the bottom of the page

I have a JS to make a smooth scroll from the bottom of the page to the top with this and it works:
<script>
$("a[href='#top']").click(function() {
$("html, body").animate({ scrollTop: 0 }, "slow");
return true;
});
</script>
But now I want to make a smooth scroll from the top to the bottom, I tried it with this:
<script>
$("a[href='#footer']").click(function() {
$("html, body").animate({ scrollToBottom: 0 }, "slow");
return true;
});
</script>`
It doesn't work, it's not a smooth scroll. Does anyone know what's wrong with this?

With pure JS:
window.scrollTo({ top: document.body.scrollHeight, behavior: 'smooth' })
and to the top as:
window.scrollTo({ top: 0, behavior: 'smooth' })

There is no such thing as scrollToBottom. Try this:
$("html, body").animate({ scrollTop: document.body.scrollHeight }, "slow");

For a more comprehensive list of methods for smooth scrolling, see my answer here.
To scroll to the bottom of the page, the y-position can be set to document.scrollingElement.scrollHeight.
For scrolling to a certain position in an exact amount of time, window.requestAnimationFrame can be put to use, calculating the appropriate current position each time. setTimeout can be used to a similar effect when requestAnimationFrame is not supported.
/*
#param pos: the y-position to scroll to (in pixels)
#param time: the exact amount of time the scrolling will take (in milliseconds)
*/
function scrollToSmoothly(pos, time) {
var currentPos = window.pageYOffset;
var start = null;
if(time == null) time = 500;
pos = +pos, time = +time;
window.requestAnimationFrame(function step(currentTime) {
start = !start ? currentTime : start;
var progress = currentTime - start;
if (currentPos < pos) {
window.scrollTo(0, ((pos - currentPos) * progress / time) + currentPos);
} else {
window.scrollTo(0, currentPos - ((currentPos - pos) * progress / time));
}
if (progress < time) {
window.requestAnimationFrame(step);
} else {
window.scrollTo(0, pos);
}
});
}
function scrollToSmoothly(pos, time) {
var currentPos = window.pageYOffset;
var start = null;
if(time == null) time = 500;
pos = +pos, time = +time;
window.requestAnimationFrame(function step(currentTime) {
start = !start ? currentTime : start;
var progress = currentTime - start;
if (currentPos < pos) {
window.scrollTo(0, ((pos - currentPos) * progress / time) + currentPos);
} else {
window.scrollTo(0, currentPos - ((currentPos - pos) * progress / time));
}
if (progress < time) {
window.requestAnimationFrame(step);
} else {
window.scrollTo(0, pos);
}
});
}
document.querySelector('button').addEventListener('click', function(e){
scrollToSmoothly(document.scrollingElement.scrollHeight, 1000);
});
html, body {
height: 5000px;
}
<button>Scroll to bottom</button>
The SmoothScroll.js library can be used as well, which handles more complex cases such as smooth scrolling both vertically and horizontally, scrolling inside other container elements, different easing behaviors, scrolling relatively from the current position, and more.
smoothScroll({yPos: 'end', duration: 1000});
document.querySelector('button').addEventListener('click', function(e){
smoothScroll({yPos: 'end', duration: 1000});
});
html, body {
height: 5000px;
}
<script src="https://cdn.jsdelivr.net/gh/LieutenantPeacock/SmoothScroll#1.2.0/src/smoothscroll.min.js" integrity="sha384-UdJHYJK9eDBy7vML0TvJGlCpvrJhCuOPGTc7tHbA+jHEgCgjWpPbmMvmd/2bzdXU" crossorigin="anonymous"></script>
<button>Scroll to bottom</button>

// Scroll smoothly to the bottom
domElement.scrollTo({
top: document.body.scrollHeight,
behavior: 'smooth',
})
All options for scrollTo are:
top: number
left: number
behavior: 'smooth' or behavior: 'auto'

The accepted answer and others are correct, but wanted to add another usecase that might help someone.
In some cases, you'd need to do the scrolling inside a setTimeout()'s callback with a short delay.
function scrollToBottom() {
window.scrollTo({ top: document.body.scrollHeight, behavior: 'smooth' });
}
setTimeout(function() { scrollToBottom(); }, 100);
For example: you have a <button> which adds a <div> element to the bottom of the page when clicked on, and you want to scroll to the bottom so the user can see this new div. In this case, sometimes (depends on the event-loop behavior), you'd need to do the scroll inside a setTimeout() because the same action that triggers the scroll actually changes the value of document.body.scrollHeight. By delaying it, you make it use the new updated value of document.body.scrollHeight after the div was added.

Keep left column visible AND scrollable

It's easy to keep a column in my layout fixed so it's always visible, even when the user scrolls down.
It's also easy to only move the column down the page when the page is scrolled down far enough for it to be out of the viewport so it's anchored before scrolling starts.
My problem is, I have left hand column that is taller than the average window so you need to be able to scroll down to see all the content (controls) in the left column but at the same time when you scroll up you want to see the top of the controls again.
Here's a visual of what I want to accomplish:
So the left column is always occupying 100% of the height of the window but as the user scrolls down they can see the bottom of the div, and when they start to scroll up the scrolls up until it reaches the top of the window again. So no matter how far they scroll the page, the top of the div is always nearby.
Is there some jQuery magic to make this happen?

Did you mean something like this? (Demo)
var sidebar = document.getElementById('sidebar');
var sidebarScroll = 0;
var lastScroll = 0;
var topMargin = sidebar.offsetTop;
sidebar.style.bottom = 'auto';
function update() {
var delta = window.scrollY - lastScroll;
sidebarScroll += delta;
lastScroll = window.scrollY;
if(sidebarScroll < 0) {
sidebarScroll = 0;
} else if(sidebarScroll > sidebar.scrollHeight - window.innerHeight + topMargin * 2) {
sidebarScroll = sidebar.scrollHeight - window.innerHeight + topMargin * 2;
}
sidebar.style.marginTop = -sidebarScroll + 'px';
}
document.addEventListener('scroll', update);
window.addEventListener('resize', update);
#sidebar {
background-color: #003;
bottom: 1em;
color: white;
left: 1%;
overflow: auto;
padding: 1em;
position: fixed;
right: 80%;
top: 1em;
}
body {
line-height: 1.6;
margin: 1em;
margin-left: 21%;
}
It almost degrades gracefully, too…

I made a fiddle for you, hope this helps you out abit.
I detect scroll up or scroll down, and set the fixed position accordion to the direction.
http://jsfiddle.net/8eruY/
CSS
aside {
position:fixed;
height:140%;
background-color:red;
width:100px;
top:20px;
left:20px;
}
Javascript
//Detect user scroll down or scroll up in jQuery
var mousewheelevt = (/Firefox/i.test(navigator.userAgent)) ? "DOMMouseScroll" : "mousewheel" //FF doesn't recognize mousewheel as of FF3.x
$('html').bind(mousewheelevt, function(e){
var evt = window.event || e //equalize event object
evt = evt.originalEvent ? evt.originalEvent : evt; //convert to originalEvent if possible
var delta = evt.detail ? evt.detail*(-40) : evt.wheelDelta //check for detail first, because it is used by Opera and FF
if(delta > 0) {
$('aside').css('top', '20px');
$('aside').css('bottom', 'auto');
}
else{
$('aside').css('bottom', '20px');
$('aside').css('top', 'auto');
}
});

http://jsfiddle.net/KCrFe/
or this:
.top-aligned {
position: fixed;
top: 10px;
}
with
var scrollPos
$(window).scroll(function(event){
var pos = $(this).scrollTop();
if ( pos < scrollPos){
$('.sidebar').addClass('top-aligned');
} else {
$('.sidebar').removeClass('top-aligned');
}
scrollPos = pos;
});

jQuery Plug-in to handle mousemove/drag with easing on a hidden div (kind of "inner zoom"

Actually I'm looking for a jQuery plug-in that can handle this:
there is a container with overflow hidden
inside of this is another one, which is way larger
when i move over the div, the part I'm seeing depends on my current position
when I'm in the left top corner I see the top left corner of the inner container
when I'm in the middle i see the middle of the container …
I wrote a little JavaScript that does that:
this.zoom.mousemove( function(event) {
var parentOffset = $(this).parent().offset();
var relativeX = event.pageX - parentOffset.left;
var relativeY = event.pageY - parentOffset.top;
var differenceX = that.zoom.width() - that.pageWidth;
var differenceY = that.zoom.height() - that.pageHeight;
var percentX = relativeX / that.pageWidth;
var percentY = relativeY / that.pageHeight;
if (1 < percentX) {
percentX = 1;
}
if (1 < percentY) {
percentY = 1;
}
var left = percentX * differenceX;
var top = percentY * differenceY;
that.zoom.css('left', -left).css('top', -top);
});
But this isn't very smooth and kinda jumpy, when you enter from another point of the container. So, before reinventing the wheel: Is there one plug in, that does exactly that and has iOS support (drag instead of mouse move)? All zoom plug ins (like Cloud Zoom) are over the top for this purpose and most have no support for dragging on iOS.
And if there's not something like this. How can I make this smoother and cooler. Any approach would be helpful. :)
Many thanks.

So, here is my solution - which works pretty well and is easy to achieve. There could be done some improvement, but to get the idea i'll leave it that way. :)
there is a demo on jsfiddle:
http://jsfiddle.net/insertusernamehere/78TJc/
CSS
<style>
div.zoom_wrapper {
position: relative;
overflow: hidden;
width: 500px;
height: 500px;
border: 1px solid #ccc;
cursor: crosshair;
}
div.zoom_wrapper > * {
position: absolute;
}
</style>
HTML
<div class="zoom_wrapper">
<img id="zoom" src="http://lorempixel.com/output/people-q-c-1020-797-9.jpg" alt="">
</div>
JAVASCRPT
<script>
var zoom = null;
// this function will work even if the content has changed
function move() {
// get current position
var currentPosition = zoom.position();
var currentX = currentPosition.left;
var currentY = currentPosition.top;
// get container size
var tempWidth = zoom.parent().width();
var tempHeight = zoom.parent().height();
// get overflow
var differenceX = zoom.width() - tempWidth;
var differenceY = zoom.height() - tempHeight;
// get percentage multiplied by difference (in pixel) cut by percentage (here 1/4) that is used as "smoothness factor"
var tempX = zoom.data('x') / tempWidth * differenceX / 4;
var tempY = zoom.data('y') / tempHeight * differenceY / 4;
// get real top and left values to move to and the last factor slows it down and gives the smoothness (and it's corresponding with the calculation before)
var left = (tempX - currentX) / 1.25;
var top = (tempY - currentY) / 1.25;
// finally apply the new values
zoom.css('left', -left).css('top', -top);
}
$(document).ready(function () {
zoom = $('#zoom');
//handle mousemove to zoom layer - this also works if it is not located at the top left of the page
zoom.mousemove( function(event) {
var parentOffset = $(this).parent().offset();
zoom.data('x', event.pageX - parentOffset.left);
zoom.data('y', event.pageY - parentOffset.top);
});
// start the action only if user is over the container
zoom.hover(
function() {
zoom.data('running', setInterval( function() { move(); }, 30) );
},
function() {
clearInterval(zoom.data('running'));
}
);
});
</script>
Note:
This one has, of course, no support for touch devices. But for that I use (again)/I can recommend the good old iScroll … :)