Develop Reference

Add/Subtract 100% of left attribute doesnt work

So I got an element with the following CSS:
top: 0;
left: 0;
width: 100%;
height: 300px;
border-radius: 0;
box-shadow: none;
transition: all .3s ease-in-out;
On click I am trying to add/subtract 100% from the left property depending on which button is clicked:
$('.next, .prev').click(function() {
if ($(this).hasClass("next")) {
$(".element").animate({
left: '-=100%'
}, 500);
}
else if ($(this).hasClass("prev")) {
$(".element").animate({
left: '+=100%'
}, 500);
}
});
When I click one of the buttons, it works fine, but on the 2nd press, it jumps to a percentage, which doesn't makes sense to me, i.e. 1002.22%, -802.222, ...
You got a full example here after clicking an element to open the content.
Does anyone know why it's not acting the way I want to?

There is no way to retrieve an elements css value as percentage, so when you try to add or subtract further it is doing this to the pixel value. I found this out when trying to do the subtraction outside of the animate call.
$('.portfolio-next, .portfolio-prev').click(function() {
var leftVal = parseFloat($(".duplicated .dupAnim").css('left'));
if ($(this).hasClass("portfolio-next")) {
leftVal = (leftVal - 100) + '%';
}
else if ($(this).hasClass("portfolio-prev")) {
leftVal = (leftVal + 100) + '%';
}
$(".duplicated .dupAnim").animate({
left: leftVal
}, 500);
});
The above code does not work, but illustrates a similar issue where the returned value is not a percentage.
In order to solve this you will probably need to keep a count (in a separate attribute or variable) of the number of times it has been added or subtracted. This is a hack and is probably not how I would choose to do it.
Alternatively there is an answer here about calculating the percentage from the pixel value that css() returns.

jQuery doesn't show and hide the header

I'm trying to make a header that appears at a certain place of the page.
So what I'm doing is checking the scroll to top of the page and the top offset of the element after which the header should appear. If the scrollTop is greater than offset the header is shown, otherwise it disappears.
But! When I scroll to the place, the header position is constantly switching between top: -13% and top: -12.999998%. After some time it finally shows the header but it never disappears.
What am I doing wrong?!
JSFiddle: https://jsfiddle.net/5k5s016f/

Well, i think the problem is that the .animate() functions are running constantly, causing the animations to "restart" before its ends.
It is not the most beautiful solution, but just adding a flag that controls the execution of the functions and a timeout to run the handler less frequently solves the problem.
https://jsfiddle.net/5k5s016f/2/
var visible = false;
$(window).scroll(function() {
setTimeout(function(){
var height = $(window).scrollTop();
var $page2 = $("#page2");
var offset = $page2.offset().top;
if (height > offset) {
if (visible) {
return;
}
visible = true;
$(".floating-header").show().animate({
top: 0
});
} else {
if (!visible) {
return;
}
visible = false;
$(".floating-header").animate({
top: "-13%"
});
}
}, 200)
});

The issue you are seeing is because each time a scroll event gets called animation queues up. If you wait long enough, you can see that the animation to set top to 0 actually works.
You can use the stop() function to stop all animation before attempting to run another one.
Something like this
if (height > offset) {
$(".floating-header").stop().show().animate({
top: "0"
}, 700);
} else {
$(".floating-header").stop().animate({
top: "-13%"
}, 700);
}
A couple of improvements I can suggest are
Debounce the scroll event handler
Check the current state of the header before queuing animation. i.e. do not try to hide it if it is already hidden and vice versa

Your logic is all messed up. Basically, you want to make sure that you are only animating when you absolutely need to - no more, no less. And since scroll events happen hundreds of times... constantly rapid firing as the user scrolls... you want to make sure you are doing the least amount of work possible during each scroll event. This especially means that you don't want to be querying the DOM on every scroll event if you don't have to (ps. $('selector') is a dom query). Take a look at this fiddle:
https://jsfiddle.net/5k5s016f/6/

Looks like I'm last to the party due to interruptions, but since I wrote it up I'll post the answer FWIW.
jsFiddle Demo
You need to debounce your code. Here is a simple system, but studing Ben Alman's explanation/examples is also recommended.
var $m1 = $('#m1'), $m2 = $('#m2'); //TESTING ONLY
var $win = $(window), $page2 = $("#page2"), $hdr=$(".floating-header");
var $offset = $page2.offset().top;
var hvis = false, curpos;
$win.scroll(function() {
curpos = $win.scrollTop();
$m1.html(curpos); //TESTING ONLY
$m2.html($offset);//TESTING ONLY
if ( curpos > $offset ) {
if ( !hvis ){
hvis = true;
//$m1.html(curpos);
$hdr.finish().animate({
top: "0"
}, 700);
}
} else {
if ( hvis ){
$hdr.finish().animate({
top: "-60px"
}, 700);
hvis = false;
}
}
});
html,
body {
height: 100vh;
width: 100vw;
}
#page1,
#page2,
#page3 {
height: 100%;
width: 100%;
background-color: #fff;
}
.floating-header {
position: fixed;
top: -60px;
background-color: #000;
width: 100%;
height: 60px;
}
.msg{position:fixed;bottom:10px;height:30px;width:80px;text-align:center;}
.msg{padding-top:10px;}
#m1 {left:3px; border:1px solid orange;background:wheat;}
#m2 {right:3px;border:1px solid green; background:palegreen;}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<header class="floating-header">Header</header>
<div id="page1">
<p>Page1</p>
</div>
<div id="page2">
<p>Page2</p>
</div>
<div id="page3">
<p>Page3</p>
</div>
<div id="m1" class="msg"></div>
<div id="m2" class="msg"></div>

jquery - moving multiple instances of div across screen at random Y-position

I want to detect clicks and move elements from off-screen right to off-screen left with jquery.
I achieved the general idea already (fiddle) but only for one div, once.
HTML:
<div class = "outer">
<div id = "box">
</div>
</div>
CSS:
body {
overflow-x: hidden;
height: 500px;
}
#box{
height: 100px;
width: 100px;
background: #FF00FF;
position: absolute;
right: -100px;
}
JS:
$(document).ready(function(){
$(document).click(function(){
var bodyHeight = document.body.clientHeight;
var randPosY = Math.floor((Math.random()*bodyHeight));
$('#box').css('top', randPosY);
$("#box").animate({left: '-100px'}, 5000);
});
});
How can make a new instance div appear (at random y-position) per click on the document?
My random y-position is calculated in jQuery the following way, but gets its value from my css height: 500px; - how can I make this value responsive?

Use a function constructor to add object instances of a div, where each one uses .box class instead of #box:
fiddle
function SlidingDiv(bodyHeight){
this.randPosY = Math.floor((Math.random()*bodyHeight));
this.$div = $("<div>").addClass('box').appendTo('.outer');
};
SlidingDiv.prototype.slide = function(){
this.$div.css('top', this.randPosY);
this.$div.animate({left: '-100px'}, 5000);
};
$(document).ready(function(){
$(document).click(function(){
var bodyHeight = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight;
var div = new SlidingDiv(bodyHeight);
div.slide();
});
});
Edit: To remove divs, you could try the complete function:
SlidingDiv.prototype.slide = function() {
this.$div.css('top', this.randPosY);
this.$div.animate({
left: '-100px',
duration: 5000,
complete: function() { this.$div.remove(); }.bind(this)
});
};

How do I script such that my panoramic image can be panned left and right up to its edges?

Say my image (panoramic) is 10,000 pixels long, but I want to be able to view only 1000 pixels wide at a time, and in order to view more of it, I can just hover my mouse either left or right, and then the image will move accordingly please? If possible, a simple script on HTML? (I'm not sure how to use Javascript or CSS, but if it needs to come down to that, do guide me step by step?
Thank you.

Here is a simple JQuery which you can use to scroll the whole page when hovering over either the left or right;
Example - https://jsfiddle.net/38da9pca/
Need any help implementing it just leave a comment and I will try and help you.
$(function() {
$('#right').on('mouseenter', rscroll);
$('#left').on('mouseenter', lscroll);
$('#right, #left').on('mouseleave', function() {
$('body').stop();
});
function rscroll() {
$('body').animate({
scrollLeft: '+=25'
}, 10, rscroll);
}
function lscroll() {
$('body').animate({
scrollLeft: '-=25'
}, 10, lscroll);
}
});
Edit (Scroll Image Only)
Example - https://jsfiddle.net/38da9pca/1/
I have change it so the lscroll and the rscroll will effect the id of image instead of the body and change it from scrollLeft to left, and that way it will move the images scroll. Dont forgot to change the $('body').stop(); to $('#bg').stop(); or it will never stop scrolling
$(function() {
$('#right').on('mouseenter', rscroll);
$('#left').on('mouseenter', lscroll);
$('#right, #left').on('mouseleave', function() {
$('#bg').stop();
});
function rscroll() {
$('#bg').animate({
left: '-=25'
}, 10, rscroll);
}
function lscroll() {
$('#bg').animate({
left: '+=25'
}, 10, lscroll);
}
});

Here's one. It's using jquery (javascript library). You would have to add it in order to make it work.
Example:
http://www.gayadesign.com/scripts/jqueryphotonav/
Tutorial:
https://blog.gaya.ninja/articles/jquery-convertion-panoramic-photoviewer-in-javascript/

Something like this?
var imgView = document.querySelectorAll('.img-view')[0];
var img = imgView.querySelectorAll('img')[0];
imgView.onmousemove = function(e) {
var x = e.clientX;
var px = ((x / this.offsetWidth) * 100);
var ix = ((px / 100) * img.offsetWidth);
img.style.left = '-' + (ix - this.offsetWidth) + 'px';
}
.img-view {
width: 256px;
height: 160px;
overflow: hidden;
position: relative;
border: 1px solid #ddd;
}
.img-view img {
height: 100%;
position: relative;
top: 0;
left: 0;
}
<div class="img-view">
<img src="http://panoramalove.com/wp-content/uploads/2013/01/nighttime-panoramic-view-of-hong-kong-island-from-the-avenue-of-stars-in-tsim-sha-tsui.jpg">
</div>

Adjustable page division boundary

I have two columns in my HTML page.
<div id="content">
<div id="left"></div>
<div id="right"></div>
</div>
Each of them occupies half of the page
#content {
height: 100%;
}
#left, #right {
float: left;
width: 50%;
height: 100%;
overflow: auto;
}
I'd like the boundary between left and right halves to be adjustable by the user. That is, the user can move the boundary to the left or to the right as he/she browses the page. Is it possible to do that somehow?

Yes, but it requires JavaScript. To apply it, you could of course just set the width of each of the sides:
var leftPercent = 50;
function updateDivision() {
document.getElementById('left').style.width = leftPercent + '%';
document.getElementById('right').style.width = (100 - leftPercent) + '%';
}
Now you can adjust the division with, say leftPercent = 50; updateDivision(), but the user isn't going to do that. There are multiple different ways you could present this to the user. Probably the best-suited way would be a little line in the middle they could drag. For this, you could use a little CSS for the positioning:
#content {
position: relative;
}
#divider {
position: absolute;
/* left to be set by JavaScript */
width: 1px;
top: 0;
bottom: 0;
background: black;
cursor: col-resize;
/* feel free to customize this, of course */
}
And then make sure you've got a div with an id of divider in content and update updateDivision to also update the left of divider:
document.getElementById('left').style.left = leftPercent + '%';
Then you just need a little logic to handle the dragging. (Here, I've put all of the elements into appropriately-named variables):
divider.addEventListener('mousedown', function(e) {
e.preventDefault();
var lastX = e.pageX;
document.documentElement.addEventListener('mousemove', moveHandler, true);
document.documentElement.addEventListener('mouseup', upHandler, true);
function moveHandler(e) {
e.preventDefault();
e.stopPropagation();
var deltaX = e.pageX - lastX;
lastX = e.pageX;
leftPercent += deltaX / parseFloat(document.defaultView.getComputedStyle(content).width) * 100;
updateDivision();
}
function upHandler(e) {
e.preventDefault();
e.stopPropagation();
document.documentElement.removeEventListener('mousemove', moveHandler, true);
document.documentElement.removeEventListener('mouseup', upHandler, true);
}
}, false);
You should be able to read it to see how it works, but in short: It listens for when someone presses on the divider. When they do, it'll attach listeners to the page for when they move their mouse. When they do, it updates the variable and calls updateDivision to update the styles. When eventually it gets a mouseup, it stops listening on the page.
As a further improvement, you could make every element have an appropriate cursor style while dragging so your cursor doesn't flash while dragging it.
Try it out.

There's nothing in the divisions so nothing will happen. It's like writing:
<h1></h1>
And changing the CSS for h1 and expecting something to be there