We Keep Coding

jQuery - Technics for reduce code in on scroll function

i have often Code like this and i think there is for sure a way to write it shorter. I would be glad to learn some new technic if there is one =)
please remind it´s inside an on scroll function. Each block is for one layer that is scrolled sideways.
st : is the actuel scrollTop()
cat3 : scrollTop of content before 3*wh in this case
cat4 : scrollTop of content before + width of cat3
cat5 : scrollTop of content before + width of layer1 + width of cat4
...
var w3 = st - (3 * wh);
if (w3 > 0) {
$('#cat3 .inside').css({
"left" : -1 * w3 + "px",
"position" : "fixed"
});
} else if (w3 < 0){
$('#cat3 .inside').css({
"left" : "0",
"position" : "absolute"
});
}
var w4 = st - (3 * wh + fh[3]);
if (w4 > 0) {
$('#cat4 .inside').css({
"left" : -1 * w4 + "px",
"position" : "fixed"
});
} else if (w4 < 0){
$('#cat4 .inside').css({
"left" : "0",
"position" : "absolute"
});
}
var w5 = st - (3 * wh + fh[3] + fh[4]);
if (w5 > 0) {
$('#cat5 .inside').css({
"left" : -1 * w5 + "px",
"position" : "fixed"
});
} else if (w5 < 0){
$('#cat5 .inside').css({
"left" : "0",
"position" : "absolute"
});
}
Thank you for your advices!

Perhaps wrap the repetitive code in a function:
function setScroll(value, selector) {
var element = $(selector + ' .inside');
var left, position;
if (value > 0) {
left = -1 * value + "px";
position = 'fixed';
} else if (value < 0){
left = 0;
position = 'absolute';
}
element.css({left, position});
}
var w3 = st - (3 * wh);
var w4 = st - (3 * wh + fh[3]);
var w5 = st - (3 * wh + fh[3] + fh[4]);
setScroll(w3, '#cat3');
setScroll(w4, '#cat4');
setScroll(w5, '#cat5');
element.css({left, position}); is ES6 syntax, if for whatever reason you can't use ES6, replace this line with:
element.css({
left: left,
position: position
});
The trick is to identify which parts change, and which parts do not. I identified only two things change here: The value you're comparing with 0, and the element you're modifying.

here is my each function. now its total felxible in amount of cats.
f is calculated once outside of the onScroll function. Any suggestions to this? Thanks.
$('.side-scroll').each(function() {
c[n] = st - (f[n]);
setScroll(c[n], '#cat' + n);
n++;
if(n == ss ){n = 0;}
});

on scroll div gradually fadein fadeout

I am trying to creating fadein fadeout effect with scrolling but not figure out how . it is like http://www.popsci.com/ . There If scroll then background image (div id fixed-image ) get fading. Them code something like. But I cannot figure out yet how to easily apply in my code. Would guys please check it my code .
var opacity = 1;
var img = element.find('img');
// Look for featured stories.
if (element.length > 0) {
// Attach background image element.
$('#page-wrapper').prepend('<div id="fixed-image" style="background-image: url(\'' + img.attr('data-lgsrc') + '\');"></div>');
img.addClass('hidden');
var scrollPercent;
$(window).scroll(function() {
// When User scrolls down, determine percentage from top to bottom of window.
scrollPercent = (($(window).scrollTop() / $(window).height() * 1.9) - 0.9);
if (scrollPercent < 0) {
$('#fixed-image').css({
'-webkit-filter' : 'blur(0px)',
'-moz-filter' : 'blur(0px)',
'-o-filter' : 'blur(0px)',
'-ms-filter' : 'blur(0px)',
'filter' : 'blur(0px)'
});
}
var opacityCount = 1.5 - Math.min(1.5, (scrollPercent + 1));
$('#fixed-image').css('opacity', opacityCount);
if (scrollPercent <= 1) {
$('#fixed-image').css('opacity', opacityCount);
$('#fixed-image').css({
'-webkit-filter' : 'blur(' + scrollPercent * 10 + 'px)',
'-moz-filter' : 'blur(' + scrollPercent * 10 + 'px)',
'-o-filter' : 'blur(' + scrollPercent * 10 + 'px)',
'-ms-filter' : 'blur(' + scrollPercent * 10 + 'px)',
'filter' : 'blur(' + scrollPercent * 10 + 'px)'
});
}
else {
$('.content-wrapper-outer').css('background-color', 'rgba(255,255,255,' + opacity + ')');
my demo is here https://jsfiddle.net/cyber007/6e6dbr6j/1/
i want slider class will be fadeIn and fadeout gradually base on scrolling
UPDATE
$(window).scroll(function(){
$(".slider").css("opacity", 1 - $(window).scrollTop() / 250);
});
https://jsfiddle.net/cyber007/6e6dbr6j/2/ this one work fine. jus one minor think in console i saw that opacity value keep running after 0 even going - value. i don't think after value 0 no need down value more

Here's a function to clip opacity at 0, although according to MDN: "Any value outside the interval [0 to 1], though valid, is clamped to the nearest limit in the range," so it's not strictly necessary.
$(window).scroll(function(){
var opacity = 1 - $(window).scrollTop() / 250;
if (opacity < 0 ) opacity = 0;
$(".slider").css("opacity", opacity);
});
UPDATE
For arbitrary start and end of your transition, use the linear equation , like so:
$(window).scroll(function(){
var start = 200, end = 600;
var opacity = 1 - ($(window).scrollTop() - start) / (end - start);
if (opacity > 1 ) opacity = 1;
if (opacity < 0 ) opacity = 0;
$(".slider").css("opacity", opacity);
});
Here's a JSFiddle.

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.

Want the script corrected not to change the size of images

I want this script not to change the sizes of the images but the same sizes anywhere they are during sliding. The issue is somewhere in this code but i don't know which one that is changing the size. I want an even size
/**
* Given the item and position, this function will calculate the new data
* for the item. One the calculations are done, it will store that data in
* the items data object
*/
function performCalculations($item, newPosition) {
var newDistanceFromCenter = Math.abs(newPosition);
// Distance to the center
if (newDistanceFromCenter < options.flankingItems + 1) {
var calculations = data.calculations[newDistanceFromCenter];
} else {
var calculations = data.calculations[options.flankingItems + 1];
}
var distanceFactor = Math.pow(options.sizeMultiplier, newDistanceFromCenter)
var newWidth = distanceFactor * $item.data('original_width');
var newHeight = distanceFactor * $item.data('original_height');
var widthDifference = Math.abs($item.width() - newWidth);
var heightDifference = Math.abs($item.height() - newHeight);
var newOffset = calculations.offset
var newDistance = calculations.distance;
if (newPosition < 0) {
newDistance *= -1;
}
if (options.orientation == 'horizontal') {
var center = data.containerWidth / 2;
var newLeft = center + newDistance - (newWidth / 2);
var newTop = options.horizon - newOffset - (newHeight / 2);
} else {
var center = data.containerHeight / 2;
var newLeft = options.horizon - newOffset - (newWidth / 2);
var newTop = center + newDistance - (newHeight / 2);
}
var newOpacity;
if (newPosition === 0) {
newOpacity = 1;
} else {
newOpacity = calculations.opacity;
}
// Depth will be reverse distance from center
var newDepth = options.flankingItems + 2 - newDistanceFromCenter;
$item.data('width',newWidth);
$item.data('height',newHeight);
$item.data('top',newTop);
$item.data('left',newLeft);
$item.data('oldPosition',$item.data('currentPosition'));
$item.data('depth',newDepth);
$item.data('opacity',newOpacity);
}
function moveItem($item, newPosition) {
// Only want to physically move the item if it is within the boundaries
// or in the first position just outside either boundary
if (Math.abs(newPosition) <= options.flankingItems + 1) {
performCalculations($item, newPosition);
data.itemsAnimating++;
$item
.css('z-index',$item.data().depth)
// Animate the items to their new position values
.animate({
left: $item.data().left,
width: $item.data().width,
height: $item.data().height,
top: $item.data().top,
opacity: $item.data().opacity
}, data.currentSpeed, options.animationEasing, function () {
// Animation for the item has completed, call method
itemAnimationComplete($item, newPosition);
});
} else {
$item.data('currentPosition', newPosition)
// Move the item to the 'hidden' position if hasn't been moved yet
// This is for the intitial setup
if ($item.data('oldPosition') === 0) {
$item.css({
'left': $item.data().left,
'width': $item.data().width,
'height': $item.data().height,
'top': $item.data().top,
'opacity': $item.data().opacity,
'z-index': $item.data().depth
});
}
}
}

random position of divs in javascript

I'm trying to make Divs to appear randomly anywhere on a webpage with javascript. So a div appears then disappears, then another div appears somewhere else on the page then disappears, then another div appears again in another random spot on the page then disappears, and so on.
I'm not sure on how to generate random units in pixels or what technique to use to generate random positions.
How do I do that? Here's my code:
var currentDivPosition = myDiv.offset(),
myDivWidth = myDiv.width(),
myDivHeight = myDiv.height(),
var myDiv = $('<div>'),
finalDivPositionTop, finalDivPositionLeft;
myDiv.attr({ id: 'myDivId', class: 'myDivClass' }); // already defined with position: absolute is CSS file.
// Set new position
finalDivPositionTop = currentDivPosition.top + Math.floor( Math.random() * 100 );
finalDivPositionLeft = currentDivPosition.left + Math.floor( Math.random() * 100 );
myDiv.css({ // Set div position
top: finalDivPositionTop,
left: finalDivPositionLeft
});
$('body').append(myDiv);
myDiv.text('My position is: ' + finalDivPositionTop + ', ' + finalDivPositionLeft);
myDiv.fadeIn(500);
setTimeout(function(){
myDiv.fadeOut(500);
myDiv.remove();
}, 3000);

Here's one way to do it. I'm randomly varying the size of the div within a fixed range, then setting the position so the object is always placed within the current window boundaries.
(function makeDiv(){
// vary size for fun
var divsize = ((Math.random()*100) + 50).toFixed();
var color = '#'+ Math.round(0xffffff * Math.random()).toString(16);
$newdiv = $('<div/>').css({
'width':divsize+'px',
'height':divsize+'px',
'background-color': color
});
// make position sensitive to size and document's width
var posx = (Math.random() * ($(document).width() - divsize)).toFixed();
var posy = (Math.random() * ($(document).height() - divsize)).toFixed();
$newdiv.css({
'position':'absolute',
'left':posx+'px',
'top':posy+'px',
'display':'none'
}).appendTo( 'body' ).fadeIn(100).delay(1000).fadeOut(500, function(){
$(this).remove();
makeDiv();
});
})();
Edit: For fun, added a random color.
Edit: Added .remove() so we don't pollute the page with old divs.
Example: http://jsfiddle.net/redler/QcUPk/8/

Let's say you have this HTML:
<div id="test">test div</div>
And this CSS:
#test {
position:absolute;
width:100px;
height:70px;
background-color:#d2fcd9;
}
Using jQuery, if you use this script, whenever you click the div, it will position itself randomly in the document:
$('#test').click(function() {
var docHeight = $(document).height(),
docWidth = $(document).width(),
$div = $('#test'),
divWidth = $div.width(),
divHeight = $div.height(),
heightMax = docHeight - divHeight,
widthMax = docWidth - divWidth;
$div.css({
left: Math.floor( Math.random() * widthMax ),
top: Math.floor( Math.random() * heightMax )
});
});
The way this works is...first you calculate the document width and height, then you calculate the div width and height, and then you subtract the div width from the document width and the div height from the document height and consider that the pixel range you're willing to put the div in (so it doesn't overflow out of the document). If you have padding and border on the div, you'll need to account for those values too. Once you've figured out the range, you can easily multiple that by Math.random() and find the random position of your div.
So once more: first find the dimensions of the container, then find the dimensions of your element, then subtract element dimensions from container dimensions, and THEN use Math.random() on that value.
The basic idea is encapsulated here:
http://jsfiddle.net/5mvKE/

Some bugs:
You missed to position the div absolutely. Otherwise it will not
work.
I think you need to ad 'px' to the numbers.
The map is made of strings
Right in your jQuery css setup:
myDiv.css({
'position' : 'absolute',
'top' : finalDivPositionTop + 'px',
'left' : finalDivPositionLeft + 'px'
});

I changed an existant code by this one for our website, you can see it on tweefox.nc
<script>
function draw() {
$(canvas).attr('width', WIDTH).attr('height',HEIGHT);
con.clearRect(0,0,WIDTH,HEIGHT);
for(var i = 0; i < pxs.length; i++) {
pxs[i].fade();
pxs[i].move();
pxs[i].draw();
}
}
function Circle() {
this.s = {ttl:8000, xmax:10, ymax:4, rmax:10, rt:1, xdef:950, ydef:425, xdrift:4, ydrift: 4, random:true, blink:true};
this.reset = function() {
this.x = (this.s.random ? WIDTH*Math.random() : this.s.xdef);
this.y = (this.s.random ? HEIGHT*Math.random() : this.s.ydef);
this.r = ((this.s.rmax-1)*Math.random()) + 1;
this.dx = (Math.random()*this.s.xmax) * (Math.random() < .5 ? -1 : 1);
this.dy = (Math.random()*this.s.ymax) * (Math.random() < .5 ? -1 : 1);
this.hl = (this.s.ttl/rint)*(this.r/this.s.rmax);
this.rt = Math.random()*this.hl;
this.s.rt = Math.random()+1;
this.stop = Math.random()*.2+.4;
this.s.xdrift *= Math.random() * (Math.random() < .5 ? -1 : 1);
this.s.ydrift *= Math.random() * (Math.random() < .5 ? -1 : 1);
}
this.fade = function() {
this.rt += this.s.rt;
}
this.draw = function() {
if(this.s.blink && (this.rt <= 0 || this.rt >= this.hl)) {
this.s.rt = this.s.rt*-1;
this.dx = (Math.random()*this.s.xmax) * (Math.random() < .5 ? -1 : 1);
this.dy = (Math.random()*this.s.ymax) * (Math.random() < .5 ? -1 : 1);
} else if(this.rt >= this.hl) this.reset();
var newo = 1-(this.rt/this.hl);
con.beginPath();
con.arc(this.x,this.y,this.r,0,Math.PI*2,true);
con.closePath();
var cr = this.r*newo;
g = con.createRadialGradient(this.x,this.y,0,this.x,this.y,(cr <= 0 ? 1 : cr));
g.addColorStop(0.0, 'rgba(255,255,255,'+newo+')');
g.addColorStop(this.stop, 'rgba(255,255,255,'+(newo*.2)+')');
g.addColorStop(1.0, 'rgba(255,255,255,0)');
con.fillStyle = g;
con.fill();
}
this.move = function() {
this.x += (this.rt/this.hl)*this.dx;
this.y += (this.rt/this.hl)*this.dy;
if(this.x > WIDTH || this.x < 0) this.dx *= -1;
if(this.y > HEIGHT || this.y < 0) this.dy *= -1;
}
this.getX = function() { return this.x; }
this.getY = function() { return this.y; }
}
$(document).ready(function(){
// if( /Android|AppleWebKit|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(navigator.userAgent) ) {
// } else {
if(document.getElementById('pixie')) {
WIDTH = $(window).width();
HEIGHT = $(window).height();
canvas = document.getElementById('pixie');
$(canvas).attr('width', WIDTH).attr('height',HEIGHT);
con = canvas.getContext('2d');
pxs = new Array();
rint = 60;
for(var i = 0; i < 50; i++) {
pxs[i] = new Circle();
pxs[i].reset();
}
setInterval(draw,rint);
}
// }
});
</script>