Develop Reference

How to make a preloader before web page even loaded?

I'd like to make a preloader bar that shows how much the page is loading before it is fully loaded (something like pushcollective.com, notice the upper bar before the page is fully load).
How can I achieve something like this? I imagine directing the user into a loading page first and request the page using AJAX and put the requested content into a div after it has finished loading. But I don't think that's a clean solution?

The website you provided a link to (http://pushcollective.com/) uses NProgress.js plugin. As far as I was able to explore it uses random values to increment the progress bar (IMHO not a very elegant solution but I guess the only possible).
Here is a snippet from plugins code:
/**
* Increments by a random amount.
*/
NProgress.inc = function(amount) {
var n = NProgress.status;
if (!n) {
return NProgress.start();
} else {
if (typeof amount !== 'number') {
amount = (1 - n) * clamp(Math.random() * n, 0.1, 0.95);
}
n = clamp(n + amount, 0, 0.994);
return NProgress.set(n);
}
};

I personally wouldn't think of what I'm about to propose as of a 'clean' solution, however here's another approach without an extra AJAX call to load the page:
Separate your content into two parts: a progress bar and everything else (which would be an actual page content). The progress bar is never-ending, filling logarithmically. The filling logic should be in an tag placed right after your progress bar inside the . That way it will start working before everything's loaded, but after the progress bar appears.
Make the "actual content" block hidden initially. Subscribe to DOM Ready event. When it fires, hide the progress and show the content. Or you can show full progress for a split of a second and then hide it.
I don't think of the above as of 'clean', because it doesn't reflect actual progress, but it doesn't seem to do so in example you've mentioned either.

Recently I came across with this simple and easy to use plugin for jQuery call PreLoadMe, I find it the Best so far:
http://niklausgerber.com/blog/preloadme-a-lightweight-jquery-website-preloader/

Well, I ended with pacejs, it's pretty cool, easy to use, and easy to configure. You guys can check it out here, thanks for all the answer.

Infinite Scroll + Swipe.js

Background:
I'm making a portfolio site utilising both Swipe.js and Infinite Ajax Scroll (JQ).
Problem:
When the content from extra pages is loaded into the current page, it is not processed by the already-loaded Swipe.js script. This means that the new content doesn't have it's mark-up changed (needed for the swipe functionality to work).
I think I need to get the Swipe.js script to fire after each page re-load. Would that fix it? Please explain this to me like I'm an 8yr old. JS is not a strong suit...
Demo:
http://hatchcreative.co.nz/tomo
You can see that as the page loads new content, the buttons on either side of the sliders no longer work.

Yes you're right, after the images are loaded you have to create a new Swipe instance on these new elements (as they weren't there at the beginning, when the page was loaded).
Based on the docs of infinite scroll you can use onRenderComplete.
So you had your jQuery.ias constructor like this:
jQuery.ias({
// ... your settings...
onRenderComplete: function(items) {
$(items).each(function(index, element) {
new Swipe(element);
});
}
});
This should work this way somehow, but I am not exactly sure; I haven't worked with these libraries yet.
Edit:
After some more inspection of your code, I saw you had some inline click handler like: onclick='two.prev();return false;'.
You need to remove this and add your onclick handle in the same onRenderComplete function.
onRenderComplete: function(items) {
var swipe;
$(items).each(function(index, element) {
swipe = new Swipe(element);
});
// find tags with the class 'forward' inside the current element and add the handler
$(element).find('.forward').on('click', function() {
swipe.next();
});
// ... also for previous
}
By the way: Usually you should provide a jsFiddle with your important code parts, so it's easier for us to get the problem, and the question is not getting obsolote when the linked page changes.

shadowbox stops working after jquery function call

I have a shadowbox script. When I load the page everything works fine, but when I call this jquery load function and then try to trigger the shadowbox by clicking on the image, the large image opens in new window instead.
Here's the code:
<link href="CSS/main.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="shadowbox-3.0.3/shadowbox.js"></script>
<script type="text/javascript">
Shadowbox.init();
</script>
<p id="compas"></p>
Any idea why this is happening?

EDIT
So, we finally get the bottom of this. 15 hours after first commenting on this issue, and at least 50 iterations later, we finally have identified what the problem is and how to fix it.
It actually struck me suddenly when I was creating local aaa.html and bbb.html on my server. That was when it hit me that the element nodes for the content that was being replaced was being removed altogether from the DOM when $.load() runs the callback function. So, once the #menu-home content elements were replaced, they were removed from the DOM and no longer had Shadowbox applied to them.
Once I figured this out, it was just a matter of a single web search and I found:
Nabble-Shadowbox - Reinit Shadowbox
Specifically, the response from mjijackson. What he describes is how to "restart" (reinitialize) Shadowbox using:
Shadowbox.clearCache();
Shadowbox.setup();
So once the #menu-home content was reloaded, what needs to happen is the Shadowbox cache needs to be cleared (essentially, shutting it down on the page), then the Shadowbox.setup() is run, which will detect the elements all over again. You don't run the Shadowbox.init() method again either.
I noticed that you had tried to copy/paste the Shadowbox.setup() in after the $.load(), at least sequentially in the code. However, this wasn't going to work, due to the cache clearing that needs to happen first, and primarily because the .clearCache() and .setup() functions need to be run after the $.load() completes (finishes and runs any callbacks). Those two functions need to be run in the $.load() callback handler; otherwise, you're running it's immediately, but the $.load() is asynchronous and will complete at some later time.
I'm going to go over some other changes I made, just so you understand what, why and wherefore.
Note, I'm not sure if you're familiar with <base>, but the following is at the top of the HEAD element:
<base href="http://62.162.170.125/"/>
This just let's me use the resource files on your computer. You'll not want to use this on your actual site more than likely. If you copy/paste, make sure and remove this line.
<div id="menu">
<ul>
<li><a id="menu-home" href="index.html" rel="http://jfcoder.com/test/homecontent.html">Home</a></li>
<li><a id="menu-services" href="services.html" rel="http://jfcoder.com/test/servicescontent.html">Services</a></li>
<li><a id="menu-tour" href="tour.html" rel="http://jfcoder.com/test/tourcontent.html">Tour</a></li>
<li><a id="menulogin" href="login.html">Login</a></li>
</ul>
</div>
Here, you'll notice I have a relative url in the HREF attribute, and a link to some pages on my server. The reason for the links to my server is that I couldn't access your aaa.html and bbb.html files through AJAX due to cross-site scripting limitations. The links to my website should be removed as well.
Now, the reason I'm using the rel attribute here is that I want allow for the links by way of the href attribute to continue to work in case the JS doesn't function correctly or there's some other error. If you have separate files, one for full HTML document and another for just the fragments, this is what you'll want to do. If you can serve both the full document AND the content-only from the linked file, then you probably don't need the rel attribute, but you'll need to manage the request so the server knows how to respond (full document or just the content part).
var boxInitialize = function(){
try {
if (!Shadowbox.initialized) {
Shadowbox.init();
Shadowbox.initialized = true;
} else {
Shadowbox.clearCache();
Shadowbox.setup();
}
} catch(e) {
try {
Shadowbox.init();
} catch(e) {};
}
};
All I've done here is create a central location for the initialization/setup requests. Fairly straightforward. Note, I added the Shadowbox.initialized property so I could keep track of if the Shadowbox.init() had run, which can only be run once. However, keeping it all in one spot is a good idea if possible.
I also created a variable function which can be called either as a regular function:
boxInitialize();
Or as a function reference:
window.onload = boxInitialize; // Note, no () at the end, which execute the function
You'll probably notice I removed the $() and replaced them with jQuery() instead. This can turn into a real nightmare if you end up with an environment with multiple frameworks and libraries competing for $(), so it's best to avoid it. This actually just bit me real good the other day.
Since we have a closure scope within the .ready() callback, we can take advantage of that to save several "private" variables for ow use at different times in the scripts execution.
var $ = jQuery,
$content = jQuery("#content"), // This is "caching" the jQuery selected result
view = '',
detectcachedview = '',
$fragment,
s = Object.prototype.toString,
init;
Note the , at the end of all but the last line. See how I "imported" the $ by making it equal to the jQuery variable, which means you could actually use it in that#.
var loadCallback = function(response, status, xhr){
if (init != '' && s.call(init) == '[object Function]') {
boxInitialize();
}
if (xhr.success()
&& view != ''
&& typeof view == 'string'
&& view.length > 1) {
$fragment = $content.clone(true, true);
cacheContent(view, $fragment);
}
};
This runs when the $.load() completes the process of the AJAX request. Note, the content returned in the request has already been placed on the DOM by the time this runs. Note as well that we're storing the actual cached content in the $content.data(), which should never be removed from the page; only the content underneath it.
var cacheContent = function(key, $data){
if (typeof key == 'string'
&& key.length > 1
&& $data instanceof jQuery) {
$content.data(key, $data.html());
$content.data(detectcachedview, true);
}
};
cacheContent() is one a method you may not want; essentially, if it was already loaded on a previous request, then it will be cached and then directly retrieved instead of initiating another $.load() to get the content from the server. You may not want to do this; if so, just comment out the second if block in the menuLoadContent() function.
var setContent = function(html){
$content.empty().html(html);
if (init != '' && s.call(init) == '[object Function]') {
boxInitialize();
}
};
What this does is first empty the $content element of it's contents/elements, then add the specified string-based markup that we saved earlier by getting the $content.html(). This is what we'll re-add when possible; you can see once the different links have been clicked and loaded, reclicking to get that to redisplay is really quick. Also, if it's the same request as currently loaded, it also will skip running the code altogether.
(We use $content like because it is a reference to a variable containing a jQuery element. I am doing this because it's in a closure-scope, which means it doesn't show up in the global scope, but will be available for things like event handlers.
Look for the inline comments in the code.
var menuLoadContent = function(){
// This is where I cancel the request; we're going to show the same thing
// again, so why not just cancel?
if (view == this.id || !this.rel) {
return false;
}
// I use this in setContent() and loadCallback() functions to detect if
// the Shadowbox needs to be cleared and re-setup. This and code below
// resolve the issue you were having with the compass functionality.
init = this.id == 'menu-home' ? boxInitialize : '';
view = this.id;
detectcachedview = "__" + view;
// This is what blocks the superfluous $.load() calls for content that's
// already been cached.
if ($content.data(detectcachedview) === true) {
setContent($content.data(view));
return false;
}
// Now I have this in two different spots; there's also one up in
// loadCallback(). Why? Because I want to cache the content that
// loaded on the initial page view, so if you try to go back to
// it, you'll just pickup what was sent with the full document.
// Also note I'm cloning $content, and then get it's .html()
// in cacheContent().
$fragment = $content.clone(true, true);
cacheContent(view, $fragment);
// See how I use the loadCallback as a function reference, and omit
// the () so it's not called immediately?
$content.load(this.rel, loadCallback);
// These return false's in this function block the link from navigating
// to it's href URL.
return false;
};
Now, I select the relevant menu items differently. You don't need a separate $.click() declaration for each element; instead, I select the #menu a[rel], which will get each a element in the menu that has a rel="not empty rel attribute". Again, note how I use menuLoadContent here as a function reference.
jQuery("#menu a[rel]").click(menuLoadContent);
Then, at the very bottom, I run the boxInitialize(); to setup Shadowbox.
Let me know if you have any questions.
I think I might be getting to the bottom of this. I think the flaw is the way you're handling the $.load() of the new content when clicking a menu item, coupled with an uncaught exception I saw having to do with an iframe:
Uncaught exception: Unknown player iframe
This Nabble-Shadowbox forum thread deals with this error. I'm actually not getting that anymore, however I think it came up with I clicked on the tour menu item.
Now, what you're doing to load the content for the menu items really doesn't make any sense. You're requesting an entire HTML document, and then selecting just an element with a class="content". The only benefit I can see for doing this is that the page never reloads, but you need to take another approach to how to get and display the data that doesn't involve downloading the entire page through AJAX and then trying to get jQuery to parse out just the part you want.
I believe handling the content loading this way is the root cause of your problem, hence the $.load() toggling of menu views breaks your page in unexpected ways.
Question: Why don't you just link to the actual page and skip all the $.load() fanciness? Speed-wise, it won't make that much of an impact, if any at all. It just doesn't make sense to use AJAX like this, when you could just link them to the same content without issue.
There are two alternatives that would allow you to prevent roundtrip page reloads:
Setup your AJAX calls to only request the .content portion of the markup if you have the ?contentonly=true flag in the URL, not the entire HTML document. This is how it's traditionally done, and is usually relative simple to do if you have a scripting environment.
$(".content").load('index.html?contentonly=true');
Then your server responds only with the content view requested.
Serve all of the content views within the same HTML document, then show as appropriate:
var $content = $('.content');
$content.find('.content-view').hide();
$content.find('#services-content').show();
It doesn't look like you have a whole lot of content to provide, so the initial page load probably won't have that much of an impact with this particular approach. You might have to look into how to preload images, but that's a very well known technique with many quality scripts and tutorials out there.
Either one of these techniques could use the #! (hashbang) technique to load content, although I believe there are some issues with this for search engines. However, here is a link to a simple technique I put together some time ago:
http://jfcoder.com/test/hash.html
Also, this is just a tip, but don't refer to your "content" element with a class, ie, .content. There should only be one content-displaying element in the markup, right? There's not more than one? Use an id="content"; that's what ID attributes are for, to reference a single element. classes are meant to group elements by some characteristic they share, so above when I .hide() the inline content views (see #2), I look for all of the class="content-view" elements, which are all similar (they contain content view markup). But the $content variable should refer to $('#content');. This is descriptive of what the elements are.

This worked for us, we made a site that used vertical tabs and called in the pages with our shadowbox images using jQuery.load
Just give all of your anchor tags the class="sbox" and paste this script in the header.
<script>
Shadowbox.init({
skipSetup:true,
});
$(document).ready(function() {
Shadowbox.setup($('.sbox'));//set up links with class of sbox
$('a.sbox').live('click',function(e){
Shadowbox.open(this);
//Stops loading link
e.preventDefault();
});
});
</script>
Note: we had to put the .sbox class on all our rel="shadowbox" anchors as well as the on the anchor for the tab that called the .load
Thanks to this guy-> http://www.webmuse.co.uk/blog/shadowbox-ajax-and-other-generated-content-with-jquery-and-javascript/

Well, based on Shem's answer, this is my solution.
Every click on specific class, setup and open shadowbox with elements from same class:
jQuery('.sb-gallery a').live('click',function(e){
Shadowbox.setup(jQuery('.sb-gallery a'));
Shadowbox.open(this);
//Stops loading link
e.preventDefault();
});
Thanks to all

Open links in div container in JQuery Mobile

i have a multi-column layout where "#content-primary" is the div i want the actual content loaded, and "#content-secondary" holds a generated listview of links(effectively a navigation menu).
I'm using this code to change the page, pretty much following the JQM Docs, however the browser is following the links to entirely new pages, instead of loading the content from them into the "#content-primary" div. There's obviously something I'm missing.
$(function(){
$('#menu a').click(function() {
$.mobile.changePage($(this).attr('href'), {
pageContainer: $("#content-primary")
} );
});
});
Using Django on the backend, but it probably isn't relevant.

I finally found an answer here. JQuery Mobile's changePage() and loadPage() methods do too much post-processing and triggers a lot of events that really makes implementing your own dynamic loading more complicated than it should be.
The good old fashioned #("div#primary-content").load(); works, but I'm still struggling to apply JQM styles to it.

interestingly, this contradicts with this:
$.mobile.changePage() can be called
externally and accepts the following
arguments (to, transition, back,
changeHash).
And when tested this works: $.mobile.changePage("index.html", "slideup"); but this does not:
$.mobile.changePage("index.html", { transition: "slideup" });
Perhaps documentation is not quite right?

Update to the new beta 1 release

How does one disable Caching in jQuery Mobile UI

Tried...
<div data-role="page" data-cache="30">
<div data-role="page" data-cache="never">
<div data-role="page" data-cache="false">
<div data-role="page" cache="false">
Nothing seemes to work... so at the moment I'm fixing the problem on the server-side via...
.'?x='.rand()
.'&x='.rand()
I don't want to disable the AJAX just the caching. There has to be a better way though... am I missing something?
Thanks,
Serhiy

Thank you for the answers guys, and even though they didn't quite work for me they did point me in the direction to find the code I was looking for.
This is the code that I found on this gentleman's Github Gist.
https://gist.github.com/921920
jQuery('div').live('pagehide', function(event, ui){
var page = jQuery(event.target);
if(page.attr('data-cache') == 'never'){
page.remove();
};
});
There is also a back button code in that Gist, but I don't seem to need it really as my back button seems to work just fine...

Page caching is now off by default in jQM RC1. See the extract below from the jQM website about page caching: http://jquerymobile.com/demos/1.0rc1/docs/pages/page-cache.html
If you prefer, you can tell jQuery Mobile to keep previously-visited pages in the DOM instead of removing them. This lets you cache pages so that they're available instantly if the user returns to them.
To keep all previously-visited pages in the DOM, set the domCache option on the page plugin to true, like this:
$.mobile.page.prototype.options.domCache = true;
Alternatively, to cache just a particular page, you can add the data-dom-cache="true" attribute to the page's container:
<div data-role="page" id="cacheMe" data-dom-cache="true">
You can also cache a page programmatically like this:
pageContainerElement.page({ domCache: true });
The drawback of DOM caching is that the DOM can get very large, resulting in slowdowns and memory issues on some devices. If you enable DOM caching, take care to manage the DOM yourself and test thoroughly on a range of devices.

Have you tried to overwrite the default value ?
$(document).bind("mobileinit", function(){
$.mobile.page.prototype.options.domCache = false;
});
This works for me

Method 1
This disables AJAX
Read
http://jquerymobile.com/demos/1.0a2/#docs/api/globalconfig.html
Set ajaxLinksEnabled to false and it will not load and cache those pages, just work as normal links.
Method 2
Second idea is to remove cached elements. You can bind to pagehide event and make it remove the page instead. If not present in DOM, the page will be loaded again.
It can be done with this code as a proof of concept:
$('.ui-page').live('pagehide',function(){ $(this).remove(); });
But it needs a little work. The above code breaks the history. It prooves that you will only be able to use it with pages you intend to be leaves in your sitemap tree. Therefore you have to create a special selector for them or bind it to only certain pages.
Also you can bind to a button's click or mousedown event, get its href, generate page id out of it and find the div by id to remove it before jqm tries to look for it.
I have found no advised way of disabling the cache or forcing loading.

Martin's answer should be the right one in my opinion but jQuery Mobile cache the first page no matter what. https://github.com/jquery/jquery-mobile/issues/3249
I've opted to "patch" the behaviour of $.mobile.page.prototype.options.domCache = false and data-dom-cache="true"
$(document).on('pagehide', function (e) {
var page = $(e.target);
if (!$.mobile.page.prototype.options.domCache
&& (!page.attr('data-dom-cache')
|| page.attr('data-dom-cache') == "false")
) {
page.remove();
}
});

Here's my working solution:
$('.selector').live( 'pagebeforecreate', function () {
$.mobile.urlHistory.stack = [];
$.mobile.urlstack = [];
$( '.ui-page' ).not( '.ui-page-active' ).remove();
});
I wrote an (original in German) article about that topic, maybe that helps.
Link to google translated article