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Toggle class and change size on an element using jQuery

I am trying to have a div change its properties on a click function. Some of the properties I am changing with a call to toggleClass() which is fine and works great. However I also want to resize the div based on the size of the viewport. In order to have access to those numbers I am changing the width and height with jQuery. This command looks like this:
$('.box').click( function() {
$(this).toggleClass('box--grow', 0);
$(this).css('width', w * .9);
$(this).css('height', h * .9);
});
EDIT I want the height and width to go back to 100%.
I tried using the toggle class but that caused the entire div to disappear, and this solution doesn't work because when I click the div again the class is removed but the height is the same.
I am looking for a way to toggle this or to get the viewport width within the css. I tried both approaches but couldn't get anything to what I am looking for.

why not using CSS VH and VW values?
CSS:
.my90Class{
width: 90vw;
height: 90vh;
}
JS:
$('.box').click( function() {
$(this).toggleClass("my90Class");
});

You need to get the window size first, and then put everything into combined .ready() and .resize() functions, to make it responsive.
function myfunction() {
var w = $(window).width();
var h = $(window).height();
$('.box').click(function () {
if ($(this).hasClass('box--grow')) {
$(this).removeClass('box--grow');
$(this).css({
'width': '',
'height': ''
});
} else {
$(this).addClass('box--grow');
$(this).css({
'width': w * .9,
'height': h * .9
});
}
});
}
$(document).ready(myfunction);
$(window).on('resize', myfunction);
jsfiddle

You can check for the class with:
$(this).hasClass('box--grow')
Then to remove the class:
$(this).removeClass('box--grow');
And to add it back again:
$(this).addClass('box--grow');
The end would look like this save the original width and height before the event so you can add it back again:
var oldwidth = $('.box').css('width');
var oldheight = $('.box').css('height');
$('.box').click( function() {
if($(this).hasClass('box--grow')) {
$(this).removeClass('box--grow');
$('.box').css('width', oldwidth);
$('.box').css('height', oldheight);
} else {
$(this).addClass('box--grow');
}
});
untested but it would probably work

parallax.js + js fadein/out = no joy after first <li>

I am using parallax.js to animate a series of elements on a homepage. I searched for code that would allow me to add a simple "slider" effect to the elements as well.
Everything seems to be working properly, except that after the first li, the parallax effect only works horizontally. On li #1, the element hovers as expected, following the mouse in every direction.
Here's a link to jsfiddle: http://jsfiddle.net/sdeviva/t6uwq/1/
Here's a link to the revised jsfiddle: http://jsfiddle.net/sdeviva/t6uwq/5/
var scene = document.getElementById('scene');
var parallax = new Parallax(scene);
var scene = document.getElementById('scene2');
var parallax = new Parallax(scene2);
(function($) {
$.fn.ezslide = function ( options ) {
var defaults = {
fadeIn : 1000,
fadeOut : 1000,
delay : 500
},
settings = $.extend( defaults, options ),
$this = this,
cur = 0,
fadeIt = function( which ) {
var li = $this.find('li');
cur = which = (which >= li.length) ? 0 : which;
li.fadeOut( settings.fadeOut );
li.eq( which )
.delay( settings.fadeOut )
.fadeIn( settings.fadeIn, function(){
setTimeout(function() {
cur++;
fadeIt( cur );
}, settings.delay);
});
};
fadeIt( cur );
};
$('ul.scene').ezslide({
fadeIn : 600,
fadeOut : 600,
delay : 3000
});
})(jQuery);
EDIT: I sort of fixed this. I don't really know what I'm doing, so there's probably a cleaner way. But, I realized that the parallax effect was only being applied once to the first list item. The script that makes each item fade in wasn't getting the benefit of the parallax.js script.
SO - I put each fading element into its own ul, with a unique id, and a shared class. By some miracle, this actually works. But let me know if there's a better way.

This is an interesting one. The issue is that the parallax code sets the very first layer to position: relative and all others to position: absolute. This has the effect of making the parent ul have the dimensions of only the first layer. This is normally fine, except that when you display any element other than the first, the first is hidden. This causes the ul to have 0 height. The parallax depends on the height of the scene, as a result no height means no vertical movement.
You can fix the issue by applying a fixed height to your ul:
#scene{
height: 128px;
}
http://jsfiddle.net/t6uwq/7/
You can find greater detail on the motion calculation in the documentation on github.

jQuery.clone() an element, then add dynamic styling to it

Let's say I have an image, cat.jpg, and when clicked I want to clone it.
$('img.cat').on("click", function() {
$(this).clone().appendTo('#container');
});
Upon duplication, however, I want the new cat.jpg to appear as half the size of the original. And I want this to continue happening each time a new cat.jpg is clicked.
Any ideas on how to go about accomplishing this? Is it even possible to inject new styling/classes/parameters via .clone()?

It sounds like the following is what you're after:
// If all images are within #container, use $("#container") instead:
$(document).on("click", "img.cat", function () {
var original = $(this);
original.clone().css({
width: original.width() / 2,
height: original.height() / 2
}).appendTo("#container");
});
Fiddle: http://jsfiddle.net/G6XTz/
Of course, you may have wanted the newly added image to be half the size of the last cat image, rather than the cat image clicked:
Fiddle2: http://jsfiddle.net/G6XTz/1/
Caveat:
The width and height can only divide so far; eventually you'll run into some problems. Better check the result of division first, and make a decision to do something else when it makes sense.

Just setting the width to half seems to be enough with an img element, the height gets set automatically in proportion to the width:
$('#container').on('click','img.cat', function() {
$(this).clone()
.appendTo('#container')
.width(function(i,v) { return v/2;});
});
Demo: http://jsfiddle.net/Mr2x8/
But if you find you need to set the width and the height here's one way to do it:
$('#container').on('click','img.cat', function() {
var $this = $(this);
$this.clone()
.appendTo('#container')
.width($this.width()/2)
.height($this.height()/2);
});
Demo: http://jsfiddle.net/Mr2x8/1/

id do this:
$(this).clone().addClass('small').appendTo('#container');
this adds the css class small to the clone of this.

Create a new class with the specific new styling you want to get changed dynamicaly in your CSS file.
.newClass {
//example green outline
outline: solid thin green;
}
And then modify your script:
$('img.cat').on("click", function() {
$(this).clone().addClass('newClass').appendTo('#container');
});
EDIT :
If the only thing you want to change is the size of the img for lets say 10% each click then:
$('img.cat').on("click", function() {
var width = $(this).width() * 0.9;
var height = $(this).height() * 0.9;
$(this).clone().css({"width":width+"px", "height":height+"px"}).appendTo('#container');
});
The above code will produce the same image but 10% smaller than the image clicked .
If you want to click only the initial image then simply put the width and height variable outside the click function and update them inside for each click.
NOTE :
In the css() you add +"px" if initial width is in px else you add +"%" if it is in percentage.

Issue with jquery fadein

I have a piece of code here which it works but not sure why my fadein and fadeout doesn't work for the body,
If you think what the issue i'm having please let me know thanks
<script type="text/javascript">
$(window).load(function() {
var lastSlide = "";
$('#slider').nivoSlider({
effect: 'random',
directionNavHide : true,
slices : 15,
animSpeed : 500,
pauseTime : 6000,
controlNav : false,
pauseOnHover : true,
directionNav:true, //Next & Prev
directionNavHide:true, //Only show on hover
beforeChange: function(){
if(lastSlide == "images/header_used.jpg") { //use the bg image of the slide that comes before the newslide
$("body").attr("style","background: #000 url(images/bg.jpg) top center no-repeat;").fadeIn("slow");
} else {
$("body").attr("style","background: #ADADAD url(images/bgnd_grad.jpg) repeat-x;").fadeOut("slow");
}
},
afterChange: function() {
t = $(this).children("a:visible");
lastSlide = $("img", t).attr("src");
}
});
});
</script>

While it may solve your mission with the body background. i would instead have used addClass and removeClass. You are manipulating the style attribute which also show/hide uses it.
I have no way to test it but what happens if you switch the fades to show() and hide(), just to determine if delay is a factor.. :)

It my come by the fact that "lastSlide" variable could store multiple object (the one from img and the one from visible link).
t = $(this).children("a:visible");
lastSlide = $("img", t).attr("src"); //could store multiple source.
This make comparation a little bit tricker and could create bug.
Plus the fact that you use the worst way to style your body. As other says, use class or .css jQuery function (http://api.jquery.com/css/).
Hope this help

fadein and fadeout work for body,absolutely.
as Reflective said, it should be
$("body").css("background","#000 url(images/bg.jpg) top center no-repeat;").fadeOut("slow")
if still doesn't work, you may should look into your nivoSlider function

How to implement jquery like slideDown() in zepto

I am using zepto library for my mobile web site. I have recently learnt that zepto does not have slideDown() plugin like jquery. I would like to implement the same for zepto.
I have tried one on jsfiddle (http://jsfiddle.net/goje87/keHMp/1/). Here it does not animate while showing the element. It just flashes down. How do I bring in the animation?
PS: I cannot provide a fixed height because I would be applying this plugin to the elements whose height property would not be known.
Thanks in advace!!

Demo: http://jsfiddle.net/6zkSX/5
JavaScript:
(function ($) {
$.fn.slideDown = function (duration) {
// get old position to restore it then
var position = this.css('position');
// show element if it is hidden (it is needed if display is none)
this.show();
// place it so it displays as usually but hidden
this.css({
position: 'absolute',
visibility: 'hidden'
});
// get naturally height
var height = this.height();
// set initial css for animation
this.css({
position: position,
visibility: 'visible',
overflow: 'hidden',
height: 0
});
// animate to gotten height
this.animate({
height: height
}, duration);
};
})(Zepto);
$(function () {
$('.slide-trigger').on('click', function () {
$('.slide').slideDown(2000);
});
});​
​

This worked for me:
https://github.com/Ilycite/zepto-slide-transition
The Zepto Slide Transition plugin add to Zepto.js the functions bellow :
slideDown();
slideUp();
slideToggle();

Speransky's answer was helpful, and I'm offering a simplified alternative for a common drop-down navigation list, and separated into slideUp and slideDown on jsfiddle: http://jsfiddle.net/kUG3U/1/
$.fn.slideDown = function (duration) {
// show element if it is hidden (it is needed if display is none)
this.show();
// get naturally height
var height = this.height();
// set initial css for animation
this.css({
height: 0
});
// animate to gotten height
this.animate({
height: height
}, duration);
};

This would work for what you need:
https://github.com/NinjaBCN/zepto-slide-transition