jquery mobile deep dive

jQuery MobileDeep Dive

7 September 2013Culver City, California USA

Saturday, September 7, 13

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Before We Begin

• This class will move fast

• The source code is yours to keep

• The slides are available for download

What Are We Going To Do?

We are going to learn about jQuery Mobile by examining a working application. We aren’t going to decompose each line of code, instead we will examine each major area of

functionality.

Coffee Coffee+

• jQuery Mobile

• Backbone

• Responsive Design

• Templates

jQuery &jQuery Mobile

• jQuery 1.9.x

• jQuery Mobile 1.3.2

• released on July 19th

• jQuery Mobile 1.4 which will support jQuery 2.0, coming soon

Memory Management

Memory Management Tips

• Globals are bad

• Use functions for information hiding

Globals are bad

• Try to use only one global variable

• Remember: JS objects can be modified at runtime

• Use var app = app || {};

Information Hiding

• JS lacks classes or other information

• One alternative is to wrap code in anonymous functions

Performance Optimization

The fastest code is the code which is never

Performance Optimization

• JavaScript

• jQuery

• HTML

JavaScript

• Define local variables

• Be careful with closures

• Accessing object properties and array items is slower than variables

• Avoid for-in loops

jQuery

• Don’t use .live()

• Use $.mobile.activePage

• Use preventDefault()

• Cache selector

• Know when not to use jQuery

• Copy HTML collections into JS arrays

• Avoid accessing the DOM

• Use CSS classes not styles

Templates

• Think of a template like a cookie cutter

• Fill it with data, and it produces HTML

• Templates can be used on the server or on the client

• There are many templating engines

Templating Engines

• Underscore

• Handlebars

• Jade

• dust (LinkedIn)

• http://garann.github.io/template-chooser/

Handlebars

• Create a template in a script tag

• Compile template in JS

• Render template with data

Looping

• Handlebars has a built helper named, each, for looping

• else can be used with each for when no data is returned

• @index is the current loop index

• @key is the current object

Conditional

• The if helper conditionally renders a block

• else is available for falsy values

• unless inverses the logic of the if

Pre-compilation

• Precompile templates at application startup for improved performance later

• Can also ship precompiled templates using command line, node based tools

Helpers

• Handlebars allows for the creation of JS helper functions

• These handlers make it possible to extend Handlebars functionality

MV* Frameworks

• MV* Frameworks give an application structure

• It is very easy to create spaghetti code in JS

• M = model

• V = controller

• * = something else, like routing

MV* & jQuery Mobile

• jQuery Mobile and most frameworks don’t get along well

• The main reason is routing. Both JQM and MV* want to control the routes

URL Routing

• URL are an invaluable part of the internet

• Users are use to sharing them

• They provide an easy mechanism to save state in an otherwise stateless environment

Routing

• It is better for the MV* to handle routing

• To stop JQM from handling routing

•26 <script type="text/javascript"> 27 /* Prevent jQM from handling <a> clicks and # changes */ 28 /* IMPORTANT: This must be hooked before loading jQM */ 29 $(document).on("mobileinit", function () { 30 $.mobile.linkBindingEnabled = false; 31 $.mobile.hashListeningEnabled = false; 32 }); 33 </script> 34 <script src="js/libs/jquery.mobile-1.3.2.min.js" type="text/javascript"></script>

MV* Frameworks

• Angular.js, from Google

• Ember.js, based on SproutCore

• Backbone.js,

• and many more

• http://todomvc.com/

Backbone.js

• A lightweight JS library which ads structure to your client side code

• From the creator of Underscore

• Very small - 6.3k minified and gzipped

Small and Fast

• Ember.js = 56k minified

• Angular.js = 81kb minified

• http://jsperf.com/angular-vs-knockout-vs-ember/173

The Nickel Tour

• Models

• Collections

• Views

• Routes

The Happy Path

• Use extend to create a “class”

• Use built in methods like initialize

• Once the “class” is defined, use new to instantiate an object

• “Classes” begins with upper case

• Objects begins with lower case

Models

• Backbone.Model.extend()

• defaults allows for the creation of default values

Collections

• Backbone.Collection.extend()

• Use model to define the model of the collection

• Use url to define a restful api

• Backbone.View.extend()

• Use the initialize method run handler code which is executed once, like compiling templates

• Use the render method to display the view

Routes

• Backbone.Router.extend()

• Normally only one route per app

• Backbone.history.Start() tells BB to begin monitoring the URL

Unit Testing

• Many unit testing frameworks are available

• QUnit, from the jQuery Team

• YUITest, from Yahoo

• Jasmine, from Pivotal Labs

• Mocha

Unit Testing Tips

• Be sure to test logic

• Write tests before fixing bugs

• Never stop running test

• Refactor the tests, when your refactor the code

• Probably the easiest one to learn

• Used to test all of the jQuery projects

Custom Attributes

• A custom attribute is a non-standard attribute added to a tag to convey some information

• HTML has always supported custom attributes

• HTML5 makes the support explicit instead of implicit

data-*

• The official way of creating custom attributes is with data-

• Recommended is: data-<company initials>-<attribute name>

• example: data-rnc-listingId

getNamedItem()

• HTML, aka the DOM, includes the getNamedItem() method

• Returns value of the attribute node with the specified name

• /* set a click event on each row */ $(".listing").off().on("click", function () { app.CurrentListing = this.attributes.getNamedItem("data-rnc-listingid").value; });

The Viewport

Meta tags

• meta tag is an element which is used to provide structured metadata about a web page

• They can be used to specify page description, keywords, and instructions

• Always in the head section

• 5 defined attributes

Meta Tag Attributes

• name, the name of the meta tag

• content, information for the reader

• http-equiv, character encoding, auto refresh

• scheme, specifies scheme to interpret content (not support in HTML5)

• charset, added in HTML5

Examples <title>CC+</title> <meta charset="utf-8"/> <meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no, maximum-scale=1"/> <meta name="apple-mobile-web-app-capable" content="yes"/> <meta name="robots" content="noindex, nofollow">

Viewport

• A special meta tag used to provide information about the device's display

• <meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no,maximum-scale=1"/>

Viewport Parameters

• width, the width of the viewport in pixels

• initial-scale, the zoom level when the page loads

• maximum-scale, the max zoom level

• minimum-scale, the min zoom level

• user-scalable, if the user can change zoom

Tips and Tricks

• There is no standard covering the viewport

• Apple probably has the best docs

• Type carefully, no error checking on viewport

• Use the viewport standardize your app’s screen size across different devices

Responsive Design

Media Queries

• The workhorse of responsive design

• A media query is a media type and at least one expression that limits the style sheets' scope

@media screen and (min-width: 480px) and (orientation:portrait) {}

Media Query by the Piece

• The media query begins with @media

• then a media type, like screen, all, print, braille, etc

• You can add logical operators like: and, not, and only

• There is also the comma separated list which behaves like an or operator

jQuery Mobile Features

• Grids, self sizing columns which dynamically resize themselves when the size of the page changes

• Tables, added with version 1.3.0

• Panels, ala Facebook, a panel, usually options, reveals itself when an icon is clicked

Minification

Developers using other languages rarely think of the size of their code. But client side JavaScript is different. Minifying JavaScript can dramatically reduce its size and radically reduce page load time.

How to Minify

• By Hand

• Using an app

By Hand

Using an App

• packer, http://dean.edwards.name/packer/

• Microsoft Ajax Minifier, http://ajaxmin.codeplex.com/

• YUI Compressor, http://yui.github.io/yuicompressor/

• Google Closure Compiler, http://closure-compiler.appspot.com/home

In Practice

• Hand minification is fraught with danger - code is hard to read and grows increasingly fragile

• Using a web site is good for an example but not in practice, too much labor

• Usually done via a command line tool, during build or on page request

Icons and Splash Pages

• Classic icon (Microsoft)

• Standardized

• Mobile icon (Apple)

Splash Page

• An Apple thing

• The splash page is cached on the user’s device

• When the icon is click on the home page, splash page is shown while the app is loaded

HTML5 Offline App

How to Reach Me

• rockncoder@gmail.com

• http://therockncoder.blogspot.com/

• https://github.com/Rockncoder/ccplus

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