Develop Reference

Background scrolling with content matching top and bottom?

I have a page with a simple div. If the div is at the top of the page, the background image (a very long vertical wallpaper) should also only be displaying the top section. If we scroll all the way down, then at the last area way at the bottom, the bottom of the background will show. The effect is that it's like a parallax where the scrolling of the content and background image occur in tandem and are scaled to each other.
How would I do this?
Update: My attempt is something like this:
function setupMainContent(){
$("#programming").delay(1000).fadeIn(1000, function(){
$(window).scroll(function(){
var current = $(window).scrollTop();
var bottom = $(document).height() - $(window).height();
var scale = 100*(current/bottom);
$('body').css({
'background-position':scale+'%'
});
});
}
I don't really know how to work with variables within quotes however.
Update: I got it to work using this:
function setupMainContent(){
$("#programming").delay(1000).fadeIn(1000, function(){
$(window).scroll(function(){
var current = $(window).scrollTop();
var bottom = $(document).height() - $(window).height();
var scale = 100*(current/bottom) + "%";
document.body.style.backgroundPosition = "center " + scale;
});
});
}
But there seems to be very bad impact on performance. Is there any way to make it more responsive and faster?

CSS:
background-attachment: fixed;
https://developer.mozilla.org/en-US/docs/Web/CSS/background-attachment

This worked for me:
function setupMainContent(){
$("#programming").delay(1000).fadeIn(1000, function(){
$(window).scroll(function(){
var current = $(window).scrollTop();
var bottom = $(document).height() - $(window).height();
var scale = 100*(current/bottom) + "%";
document.body.style.backgroundPosition = "center " + scale;
});
*/
});
}

Finding Image Height variable for multiple images in Jquery

I'm currently working on this script for "tooltips" on a website. I'm finding that the code I currently have will get the image height for my first tooltip image on the page ('pop1') but it ignores the rest (they come out as null).
What's the most effective way to get all the tooltip image heights, and use them every time the user scrolls over the tooltip image?
Another issue, if anyone is able to figure this one out - is that on my FULL webpage (many more divs, rows, columns, etc.) the script begins to break because clientX and clientY are being affected by the various divs and page elements.
I'd like to be able to set clientX and clientY to the exact (x, y) coordinates that the user's mouse is at, relative to the entire webpage, not relative to the page's child elements.
Thanks
Here's my JSFiddle: http://jsfiddle.net/tgs7px4f/18/
JS Code:
$('a.popper').hover(function (e) {
var target = '#' + ($(this).attr('data-popbox'));
$(target).show();
}, function () {
var target = '#' + ($(this).attr('data-popbox'));
if (!($("a.popper").hasClass("show"))) {
$(target).hide();
}
});
$('a.popper').mousemove(function (e) {
var target = '#' + ($(this).attr('data-popbox'));
// images vary in height!
// images are all 366px wide.
var imageWidth = 366;
var imageHeight = $(".popimg").height();
//alert('Image Height: ' + imageHeight);
//Offset tooltip:
//10px to the right of cursor
var imageX = e.clientX + 20;
//imageHeight up from cursor
var imageY = e.clientY - imageHeight - 20;
// Find bounds of current window, and if...
// Tooltip goes off right side:
if ((imageX + imageWidth) > $(window).width()) {
//Move tooltip left so it meets edge:
imageX = $(window).width() - imageWidth;
}
// Tooltip goes off top
if (imageY < 0) {
//Move tooltip down so it meets top:
imageY = 0;
}
$(target).css('top', imageY).css('left', imageX);
});

What's the most effective way to get all the tooltip image heights, and use them every time the user scrolls over the tooltip image?
First of all, I suppose you mean whenever a user does a mouseover on one of the elements? However, this seems to work and it cashes the height of the image directly on the element and uses it the next time a mouseover occurs:
$('a.popper').mousemove(function (e) {
var target = '#' + ($(this).attr('data-popbox'));
// images vary in height!
// images are all 366px wide.
var imageWidth = 366;
$target = $(target);
if (!$target.attr("height")) {
var img = $target.closest(".popbox").children("img");
var imageHeight = img.height();
$target.attr("height", imageHeight);
console.log("height attribute set");
} else {
var imageHeight = +($target.attr("height")) + 0;
console.log("cached height used");
}
console.log('Image Height: ', imageHeight);
//Offset tooltip:
//10px to the right of cursor
var imageX = e.clientX + 20;
//imageHeight up from cursor
var imageY = e.clientY - imageHeight - 20;
// Find bounds of current window, and if...
// Tooltip goes off right side:
if ((imageX + imageWidth) > $(window).width()) {
//Move tooltip left so it meets edge:
imageX = $(window).width() - imageWidth;
}
// Tooltip goes off top
if (imageY < 0) {
//Move tooltip down so it meets top:
imageY = 0;
}
$(target).css('top', imageY).css('left', imageX);
});
Obviously, you should remove all the console.log statements which are for testing purposes only.
jsFiddle
Regarding your second question, it's hard to say anything concrete without another jsFiddle or additional code.

Change position of div based on mouse pointer

I am trying to position a div based on mouse position, I managed to get it to work 50%.
The problem is that DIV always seems to be much lower than the actual mouse position, I try to minus the offset, no luck.
Basically what I want is to float the div(the NEXT link in jsfiddle) vertically, but the DIV should not be able to go outside of the container it is in(the div that has the image in the jsfiddle)
here is the jsfiddle: http://jsfiddle.net/LYmVH/7/
below is the JS, which is also in the jsfiddle:
$('.post-single-content').mousemove(function(e){
var height=e.pageY,
height1 =$('.content-top').height();
$('.btnNext').css({top: (e.pageY + 50) + "px"});
});

You need measure against the top of the parent element since it's absolutely positioned in it.
Try changing your JS to:
$('.post-single-content').mousemove(function(e){
var top = (e.pageY - $(this).offset().top) + 'px';
$('.btnNext').css({ top: top });
});
Upon reading some comments lemme update, by making use some basic math and create "collision". Somthing like:
$('.post-single-content').mousemove(function(e){
var y = e.pageY, // mouse y axis position
tHeight = $(this).height(), // container height
bHeight = $('.btnNext').height(), // button height
oTop = $(this).offset().top, // offset top position of container
abBot = tHeight - $('.btnNext').height(), // absolute top of button when at bottom
bHalf = bHeight / 2, // half button height
top = y - oTop - bHalf, // initial top pos of button
bot = y - oTop + bHalf; // bottom of button while moving
if (top < 0) top = 0; // ensure button doesn't go to far north
else if (bot > tHeight) top = abBot; // ensure it cant go past south
$('.btnNext').css({ top: top }); // 'px' not neccesary
});
jsFiddle

Change sprites scroll speed

I'm creating a parallax website but I'm using the code of some nice tutorial that I found.
This tutorial came with some JS to change the scroll speed of some sprites using the tag "data-" but even though I already have the sprites with a different scrolling speed compared to the background, I can't modify this speed to my own preference.
This is the JavaScript code:
$(document).ready(function(){
// Cache the Window object
$window = $(window);
// Cache the Y offset and the speed of each sprite
$('[data-type]').each(function() {
$(this).data('offsetY', parseInt($(this).attr('data-offsetY')));
$(this).data('Xposition', $(this).attr('data-Xposition'));
$(this).data('speed', $(this).attr('data-speed'));
});
// For each element that has a data-type attribute
$('section[data-type="background"]').each(function(){
// Store some variables based on where we are
var $self = $(this),
offsetCoords = $self.offset(),
topOffset = offsetCoords.top;
// When the window is scrolled...
$(window).scroll(function() {
// If this section is in view
if ( ($window.scrollTop() + $window.height()) > (topOffset) &&
( (topOffset + $self.height()) > $window.scrollTop() ) ) {
// Scroll the background at var speed
// the yPos is a negative value because we're scrolling it UP!
var yPos = -($window.scrollTop() / $self.data('speed'));
// If this element has a Y offset then add it on
if ($self.data('offsetY')) {
yPos += $self.data('offsetY');
}
// Put together our final background position
var coords = '50% '+ yPos + 'px';
// Move the background
$self.css({ backgroundPosition: coords });
// Check for other sprites in this section
$('[data-type="sprite"]', $self).each(function() {
// Cache the sprite
var $sprite = $(this);
// Use the same calculation to work out how far to scroll the sprite
var yPos = -($window.scrollTop() / $sprite.data('speed'));
var coords = $sprite.data('Xposition') + ' ' + (yPos + $sprite.data('offsetY')) + 'px';
$sprite.css({ backgroundPosition: coords });
}); // sprites
// Check for any Videos that need scrolling
$('[data-type="video"]', $self).each(function() {
// Cache the video
var $video = $(this);
// There's some repetition going on here, so
// feel free to tidy this section up.
var yPos = -($window.scrollTop() / $video.data('speed'));
var coords = (yPos + $video.data('offsetY')) + 'px';
$video.css({ top: coords });
}); // video
}; // in view
}); // window scroll
}); // each data-type
}); // document ready
and this is the HTML markup of a single sprite:
<div class="stars" data-type="sprite" data-speed="10">
<img class="star1" src="img/cenas/1.PNG">
</div>
I tried changing the data-speed value but there aren't any changes. What can I do to have different sprites with different scroll speed?

Anyway to optimise this parallax script for better performance?

I have a parallax script that I am using to slow the background position of an element relative to the window scroll. It performs GREAT on my macbook pro but on slower computers it shudders more than I feel it needs to.
Here is the code below:
var bgobj = $('.paral');
$(window).scroll(function () {
onScroll(bgobj);
});
function onScroll(bgobj) {
var $window = $(window);
var yPos = ($window.scrollTop() / bgobj.data('speed'));
// Put together our final background position
var coords = yPos + 'px';
// Move the background
bgobj.css({ backgroundPositionY: coords });
}
So my question is, what optimisations can be made to the code to improve speed on lower machines?
Thank you

Have you considered throttling?
http://underscorejs.org/#throttle
http://underscorejs.org/#debounce
var bgobj = $('.paral');
var onScrollThrottled = _.throttle(onScroll, 100);
$(window).scroll(function () {
onScrollThrottled(bgobj);
});
function onScroll(bgobj) {
var $window = $(window);
var yPos = ($window.scrollTop() / bgobj.data('speed'));
// Put together our final background position
var coords = yPos + 'px';
// Move the background
bgobj.css({ backgroundPositionY: coords });
if (isScrolledIntoView($('#more-info'))) {
animateCircle();
}
}
Of course, instead of throttling/debouncing the entire onScroll function you can apply the optimisation to animateCirle or updating the background css

I see some minor improvements to be done. Nothing big:
//cache $window and speed
var $window = $(window);
var bgobj = $('.paral');
var speed = bgobj.data('speed')
$window.scroll(function () {
onScroll(bgobj);
});
function onScroll(bgobj) {
var yPos = ($window.scrollTop() / speed);
// Put together our final background position
//var coords = yPos + 'px'; // this is not needad as jQuery defaults to pixels if nothing is specified
// Move the background
bgobj.css({ backgroundPositionY: coords });
if (isScrolledIntoView($('#more-info'))) { // depending on what is inside this function, this might slow everything doen
animateCircle();
}