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JavaScript Css Animation

I have a Javascript animation at http://dev17.edreamz3.com/css/
All code works, however, there are performance problems. on Desktop, its good, On mobile things are so slow that it's unusable. I want to optimize the animation so that it runs smoothly on mobile. It can take 20 seconds or more for the animation to render.
Right now the way the code is designed is in js/anim.js there is a render() function that gets executed every time a scroll event happens. The problem is that this routine is not efficient, that's what I think of. Each time render() executes it loops through all the paths and sections of the maze and redraws them, is there any alternative way or a strategy to get it working both on mobile as well as desktop.
var offPathTime = 1000;
window.offSection = -1;
function render() {
// var top = ($window.scrollTop() + (0.4 * $window.height())) / window.scale;
var top = ($('.parent-div').scrollTop() + (0.4 * $('.parent-div').height())) / window.scale;
top -= 660;
top /= mazeSize.h;
if (window.offSection != -1) {
$body.addClass("blockScroll");
$('.parent-div').addClass("blockScroll");
// var wtop = $window.scrollTop() / window.scale;
var wtop = $('.parent-div').scrollTop() / window.scale;
wtop -= 660;
wtop /= mazeSize.h;
var $offSection = $("#offSection" + window.offSection);
var $section = $("#section" + window.offSection);
$(".section").removeClass("sectionActive");
$offSection.addClass("sectionActive");
$section.addClass("sectionActive");
var sTop = 200 -(mazeSize.h * (window.offSections[window.offSection].cy - wtop));
$container.animate({
left: 290 -(mazeSize.w * window.offSections[window.offSection].cx) + "px",
top: sTop + "px"
}, offPathTime);
// Path
var lr = offPaths[window.offSection].x1 > offPaths[window.offSection].x0;
var dx = Math.abs(offPaths[window.offSection].x1 - offPaths[window.offSection].x0);
var dashw = (dx * mazeSize.w) | 0;
$offPaths[window.offSection].css("width", "0px");
$offPaths[window.offSection].show();
if (lr) {
$offPaths[window.offSection].animate({
width: dashw + "px"
}, offPathTime);
} else {
var x0 = offPaths[window.offSection].x0 * mazeSize.w;
var x1 = offPaths[window.offSection].x1 * mazeSize.w;
$offPaths[window.offSection].css("left", x0 + "px");
$offPaths[window.offSection].animate({
width: dashw + "px",
left: x1 + "px"
}, offPathTime);
}
return;
}
$body.removeClass("blockScroll");
$('.parent-div').removeClass("blockScroll");
$(".offPath").hide();
if ($container.css("top") != "0px") {
$container.animate({
left: "-1550px",
top: "0px"
}, 500);
}
var pathIdx = -1;
var path0 = paths[0];
var path1;
var inPath = 0;
var i;
var curTop = 0;
var found = false;
for (i=0; i<paths.length; i++) {
var top0 = (i == 0) ? 0 : paths[i-1].y;
var top1 = paths[i].y;
if (top >= top0 && top < top1) {
pathIdx = i;
path1 = paths[i];
inPath = (top - top0) / (top1 - top0);
found = true;
if (i > 0) {
var dy = paths[i].y - paths[i-1].y;
var dx = paths[i].x - paths[i-1].x;
var vert = dx == 0;
if (vert)
$paths[i-1].css("height", (dy * mazeSize.h * inPath) + "px");
$paths[i-1].show();
}
} else if (top >= top0) {
path0 = paths[i];
var dy = paths[i].y - top0;
var vert = dy != 0;
if (i > 0) {
if (vert)
$paths[i-1].css("height", (dy * mazeSize.h) + "px");
$paths[i-1].show();
}
} else {
if (i > 0) {
$paths[i-1].hide();
}
}
curTop = top1;
}
// Check for an active section
$(".section").removeClass("sectionActive");
var section;
for (i=0; i<sections.length; i++) {
var d = Math.abs(sections[i].cy - (top - 0.05));
if (d < 0.07) {
var $section = $("#section" + i);
$section.addClass("sectionActive");
}
}
}

1) At the very least - assign all DOM objects to variables outside of the function scope. Like this:
var $parentDiv = $('.parent-div');
var $sections = $(".section");
...
function render() {
...
2) Also you should probably stop animation before executing it again, like this:
$container.stop(true).animate({
...
If you are running render() function on scroll - it will run many times per second. stop() helps to prevent it somewhat.
3) If it will not be sufficient - you can switch from jQuery to Zepto(jQuery-like api, but much faster and uses css transitions for animations) or to Velocity(basically drop-in replacement for jQuery $.animate and much faster than original) or even to GSAP - much more work obviously, but it is very fast and featured animation library.

Using jQuery to switch background position every 250px

I'm new to jQuery and not sure best way to change the background position, i basically need to change a background position every 0 -250px, then 0 -500px etc. What is the best way to do this?
JS:
function startAvatarAnimation() {
var avatarHeight = 250;
var avatarTotalHeight = 2750;
var i = 0;
var avatarSpeed = 1000;
setInterval(function(){
i++;
if(i > avatarArray.length){
i = 0;
}
$(".avatars").css({'background-position' : '0 -' + (i*avatarHeight) + 'px' });
}, avatarSpeed);
}
HTML:
<div class="avatars"></div>
I'm getting an error at the moment with avatarArray is not defined, this is my first attempt. I guess it needs to work out the height so it knows when to stop as well?

Fixed with the following solution:
function startAvatarAnimation() {
var avatarHeight = 250;
var avatarTotalHeight = 2750;
var i = 0;
var avatarSpeed = 500;
var avatarArray = {};
setInterval(function(){
i++;
if(i > avatarArray.length){
i = 0;
}
$(".avatars").css({'background-position' : '0 -' + (i*avatarHeight) + 'px' });
}, avatarSpeed);
}

Efficiently creating a simple parallax effect with jQuery

So for one of my new projects, I decided to write a super simple parallax script for some background images on scroll. This is what I came up with:
$(document).ready(function(){
parallaxScroll();
$(window).bind('scroll', function() {
parallaxScroll();
});
});
function parallaxScroll() {
$(".parallax").each(function() {
if($(this).hasClass('reverse')) {
$(this).css("background-position","center " + (($(this).offset().top - $(window).scrollTop())/2) + "px");
} else {
$(this).css("background-position","center " + (($(this).offset().top - $(window).scrollTop())/-2) + "px");
}
});
}
My question is, is this efficient enough? If not, is there a better solution? I wasn't sure if using an .each() would be best for performance, but it seems to work fine. The reason I have the function run at document load is so when you scroll the page for the first time, the background image doesn't jump.

Instead of css which sets the value immediately, consider using animate instead. It defers setting values using timers/requestAnimationFrame, ensuring that your animation does not block the UI, is async (runs pseudo-parallel to other code), and ensures that the animation is smooth.

This is a plain JS solution, but you'll be able to port it to jQuery really easily:
var lastScrollY = 0;
var backgroundImageY = 0;
var requestAnimationFrame = window.requestAnimationFrame ||
window.msRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.webkitRequestAnimationFrame;
window.addEventListener('load', processScrollEvent);
function processScrollEvent() {
var innerHeight = window.innerHeight;
var scrollHeight = document.body.scrollHeight;
var backgroundImage = document.querySelector('#background img');
lastScrollY = document.body.scrollTop;
var currBackgroundImageY = Math.round(((backgroundImage.scrollHeight - innerHeight) / 100) * ((lastScrollY / (innerHeight - scrollHeight)) * 100));
if(currBackgroundImageY != backgroundImageY) {
backgroundImageY = currBackgroundImageY;
requestAnimationFrame(processScrollAnimationFrame);
}
}
function processScrollAnimationFrame() {
var backgroundImage = document.querySelector('#background img');
var transforms = ['transform', 'oTransform', 'msTransform', 'mozTransform', 'webkitTransform'];
for(var i = 0; i < transforms.length; i++) {
backgroundImage.style[transforms[i]] = 'translate3d(0, ' + backgroundImageY + 'px, 0)';
}
}

How I can move DOM elements slowly?

How I can move DOM elements slowly?
This does not work
for ( var a = 0 ; a < 100 ; a++){
$('*').each(function(){
if ( ! /HTML/.test($(this).context.nodeName))
{
var top = parseInt($(this).css('top')) + 1;
$(this).css('top',top + "px");
}
});
}
Elements are positioned when the loop finish
How can I do this slowly?
Sorry for my English

Or in pure javascript, you should use a timer
var $elem = $(this), // jquery object
elem = $elem[0], // dom element
currentPos = $elem.offset().top, // current position
targetPos = currentPosition + 100, // target position
timer = setInterval (function () { // timer to move element slowly
currentPos++;
$elem.css('top',currentPosition + "px");
if (currentPos == targetPos)
clearInterval(timer);
}, 100);

try jquery's $.animate()
it requires you to set a target position to move to, rather than continuous movement
or using setInterval:
intervalInMilliseconds=17;//60 frames per second
var interval = setInterval(function()
{
for ( var a = 0 ; a < 100 ; a++){
$('*').each(function(){
if ( ! /HTML/.test($(this).context.nodeName))
{
var top = parseInt($(this).css('top')) + 1;
$(this).css('top',top + "px");
}
});
}
},intervalInMilliseconds);
stop when you're done by doing this:
clearInterval(interval)

If you are targetting new enough browser versions, you could use CSS animation instead.

javascript toggle animation issue

I am doing a small javascript animation. this is my code :
window.onload = function () {
var heading = document.getElementsByTagName('h1')[0];
heading.onclick = function () {
var divHeight = 250;
var speed = 10;
var myInterval = 0;
alert(divHeight);
slide();
function slide() {
if (divHeight == 250) {
myInterval = setInterval(slideUp, 30);
} else {
myInterval = setInterval(slideDwn, 30);
alert('i am called as slide down')
}
}
function slideUp() {
var anima = document.getElementById('anima');
if (divHeight <= 0) {
divHeight = 0;
anima.style.height = '0px';
clearInterval(myInterval);
} else {
divHeight -= speed;
if (divHeight < 0) divHeight = 0;
anima.style.height = divHeight + 'px';
}
}
function slideDwn() {
var anima = document.getElementById('anima');
if (divHeight >= 250) {
divHeight = 250;
clearInterval(myInterval);
} else {
divHeight += speed;
anima.style.height = divHeight + 'px';
}
}
}
}
i am using above code for simple animation. i need to get the result 250 on the first click, as well second click i has to get 0 value. but it showing the 250 with unchanged. but i am assigning the value to set '0', once the div height reached to '0'.
what is the issue with my code? any one help me?

Everytime you click on the div the divHeight variable is reset to 250, thus your code never calls slideDwn. Moving the divHeight declaration outside the event handler should do the trick.
Also, your div wont have the correct size when any of the 2 animations end. You're setting the divHeight variable to 250 or 0 correctly, but never actually setting anima.style.height after that.

I've rewritten your code into something simpler and lighter. The main difference here is that we're using a single slide() function here, and that the height of the div in question is stored in a variable beforehand to ensure that the element slides into the correct position.
Note that this is a very simplistic implementation and assumes that the div carries no padding. (The code uses ele.clientHeight and ele.style.height interchangeably, which admittedly, is a pretty bad choice, but is done here to keep the code simple)
var heading = document.getElementsByTagName('h1')[0],
anima = document.getElementById('anima'),
divHeight = anima.clientHeight,
speed = 10,
myInterval = 0,
animating = false;
function slide(speed, goal) {
if(Math.abs(anima.clientHeight - goal) <= speed){
anima.style.height = goal + 'px';
animating = false;
clearInterval(myInterval);
} else if(anima.clientHeight - goal > 0){
anima.style.height = (anima.clientHeight - speed) + 'px';
} else {
anima.style.height = (anima.clientHeight + speed) + 'px';
}
}
heading.onclick = function() {
if(!animating) {
animating = true;
var goal = (anima.clientHeight >= divHeight) ? 0 : divHeight;
myInterval = setInterval(slide, 13, speed, goal);
}
}
See http://www.jsfiddle.net/yijiang/dWJgG/2/ for a simple demo.

I've corrected your code a bit (See working demo)
window.onload = function () {
var heading = document.getElementsByTagName('h1')[0];
var anima = document.getElementById('anima');
var divHeight = 250;
heading.onclick = function () {
var speed = 10;
var myInterval = 0;
function slideUp() {
divHeight -= speed;
if (divHeight <= 0) {
divHeight = 0;
clearInterval(myInterval);
}
anima.style.height = divHeight + 'px';
}
function slideDwn() {
divHeight += speed;
if (divHeight >= 250) {
divHeight = 250;
clearInterval(myInterval);
}
anima.style.height = divHeight + 'px';
}
function slide() {
console.log(divHeight )
if (divHeight == 250) {
myInterval = setInterval(slideUp, 30);
} else {
myInterval = setInterval(slideDwn, 30);
}
}
slide();
}
}​