dev.chetankjain.net

Posts

jQuery Mobile and Duplicated Page IDs

In the previous post , I touched upon how browsers safely handle duplicate IDs in a html file. Things seem to work fine for the three main uses of element IDs, i.e. linking to fragments, styling and referencing the element in javascript. The first element with matching ID is picked up and styling is done for all matches. Now let us extend this test to the jQuery Mobile framework. You can launch the below multi-page code here. Launch <!DOCTYPE html> <html> <head> <title>jQuery Mobile Duplicate IDs</title> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="http://code.jquery.com/mobile/1.0.1/jquery.mobile-1.0.1.min.css" /> <script src="http://code.jquery.com/jquery-1.6.4.min.js"></script> <script src="http://code.jquery.com/mobile/1.0.1/jquery.mobile-1.0.1.min.js"...

Using duplicate IDs in HTML

Well today I'm being a bit controversial. Let us see what the HTML5 spec says about unique IDs in a HTML file. The id attribute specifies its element's unique identifier (ID) . The value must be unique amongst all the IDs in the element's home subtree and must contain at least one character. The value must not contain any space characters . An element's unique identifier can be used for a variety of purposes, most notably as a way to link to specific parts of a document using fragment identifiers, as a way to target an element when scripting, and as a way to style a specific element from CSS. Yes its been mentioned almost everywhere on the planet that ID must be unique. Now let us look at the below code, Launch dup.css #p2 { background-color: yellow; } dup-id.html <!DOCTYPE html> <html> <head> <title>Duplicate ID Tester</title> <link rel="stylesh...

jQuery Mobile Page Caching demo

In my previous post , I outlined how to prefetch links to make jQuery mobile app load your pages faster. The ui-loader spinning animation was not shown as you navigate from one page to another. Launch - The previous example with prefetch But, as also mentioned, it has certain limitations, If there are more pages, more http requests are sent out and more bandwidth is required to prefetch If a page hasn't been fully prefetched, the ui-loader spinner animation comes up till the page is fully loaded. Try to click fast and you will see Once you visit a prefetched page, navigating away from the page will remove the page from DOM. So this is not same as caching the page. The next visit to the page will again need the page to be fetched. So the obvious solution seems to be to cache the frequently visited pages in the DOM. This way, every link doesn't have to be prefetched on every visit to the page. This is easily done in jQuery Mobile by adding the attribute data-dom-cach...

jQuery Mobile Prefetching pages demo

Using a single-page template for your mobile app makes your app faster and lighter. But you have to fetch each page during navigation and you end up seeing the ui-loader spinning icon animation every time. It can get to your nerves. Launch - Example without prefetch The above example, from my previous post shows how the spinning icon comes up each time you navigate from the main page to page 2. I will not list the code here as its already listed in an earlier post . In a multi-page template whereas, the entire set of pages are already loaded into the DOM and the navigation is much faster. A similar behavior can be obtained in a single-page application by prefetching pages. This is done by just adding the attribute data-prefetch to all the links that you want to prefetch. As soon as the page loads, it starts fetching these links and loads it into the DOM. You can observe this behavior with the code inspector open (CTRL+SHIFT+I) in your browser. Now navigating to...

jQuery Mobile Page Transitions with data-ajax=false

In my earlier post here , I outlined the various page transitions that are available in jQuery Mobile. In single-page template documents, jQM uses Ajax to smoothly transition between pages and when not possible, the framework does a simple HTTP request to pull in the page. Situations where Ajax transitions are not used are: When a page loaded is: from an external domain data-ajax="false" attribute is used rel="external" is specified target attribute is specified This is also well documented (with examples) . In multi-page template documents, jQM needs Ajax to transition between the multiple page containers. Now lets play with this a bit. Let us try to override this with the data-ajax attribute and see what happens. Consider below code, you can click on the link below to launch it in a separate browser tab: Launch <!DOCTYPE html> <html> <head> <title>jQuery Mobile Transitions Demo with data-ajax="false...

Minimal required code in HTML5

I've encountered this question repeatedly of late. "What are the tags required at bare minimum for a html file?" Earlier there were a bunch of mandatory tags that were required for any html file. At bare minimum, the recommended structure was: (ref: http://www.w3.org/TR/html4/struct/global.html ) <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <HTML> <HEAD> <TITLE>A small HTML</TITLE> </HEAD> <BODY> <P>Small HTML file!</P> </BODY> </HTML> Yes, using capitals for the tags was the way to go! Those were the days of the purists and strict was the way to be. Now open your notepad and copy the above code, save the file as old.html and launch it in Chrome or Firefox. You will see only one line "Small HTML file!" shown. Now launch the developer tools in Chrome or Inspect Element in Firefox. Thi...

jQuery Mobile single-page vs multi-page template

[Updated 2012/02/09] In my recent posts I mentioned about jQuery Mobile single-page and multi-page templates, so what exactly are the differences between them? Single Page Template: Launch - example from previous post, notice the address shown as you navigate Lighter and cleaner. Each page is a separate html file and more modular. Better fallback if JavaScript is not supported. So works well on more platforms, you could even target grade C browsers On first load, the start page is loaded into the DOM. An internal reference is always held to this. Any new page loaded is added to the DOM. Any previously shown page is removed from the DOM. The start page is always in the DOM. The DOM size is relatively smaller Optional to use the "page" data-role element in the code Can turn off Ajax Navigation between pages using data-ajax="false" Recommend to use the <title> tag for page titles The <title> tag always gets precedence during page loads ...