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Backbone JS Tutorial

Jan 01 2013 Published by under Backbone, Uncategorized

Backbone JS (Stop tying your data to DOM)

Backbone.js is not a full fledged mvc or mvp or mvvm framework, Basically it provides the event bindings between the model and view, so that changes in the view will update the attributes of model and corresponding views listening to the model will get updated.

But there are many backbone js plugins, which help us to create a web application using backbone depending on the requirement. So we can implement mvc, mvp, mvvm or anything using these plugins.

What is a backbone model ? (State)

Backbone model maintains state of the application. Following things can be done in the model.

Responsibilities:

1)Getting the data from server
2)Save data to the server
3)Validation of data
4)Syncing of the data from server to client
5)Destroying the model (data,if no longer needed )

Usage:

A model has attributes to store the data, on change of any of the attribute a change event will be triggered by the model
However, this change event can also be suppressed by passing {silent:true}. views should listen to this events and display the data

Gotchas:

1)If the attribute is again a model, then the change in the attribute of the submodel will not be triggered in parent model. Use the deepModelbinderplugin.
2)Even while instantiating a model with an object, the attributes will be set and validation if exist on any attribute will trigger.
3)Becareful in specifying the initial values, if initial value is not set, then the value is treated as undefined

What is a backbone collection?

A collection is just a list of models.

Responsibilities:

1)Fetch data from server
2)Sync data to the server

Usage:

On addition or removal of model to a collection the change event will be triggered. Views should listen to this events and display the data

Gotchas:

1)While creating the collection from a model, if the validate method fails then the model will not get added into the collection

What is a backbone view ?

A view is basically UI component that displays the data to the user intutively. it interacts with the template for markup

Responsibilities:

1)listen to the model and display data when data is changed.

Gotchas:

1)Beware of zombie views, they should be destroyed and all their events should be undelegated otherwise they will become zombies

What is a backbone router?

A router allows us to configure url corresponding to the view. It should be used only to provide views as a bookmarkable url. Don’t use it as a controller.

Responsibilties:

1)It provides route and callback method corresponding to the creation of view

Usage:

Use router.navigate or Backbone.history.navigate to route to a different url. Pass {trigger:true} to trigger the callback method corresponding to the view

Gotachs:

1)By default callback corresponding to the empty route will be called.
2)This is not a controller and never should be used a controller. it should not be passed to the views. use Backbone.history.navigate() method for such cases.

P.S: This post is for developers, who are new to backbone. Shortly, Continue Reading »

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Sass & Compass

Jun 04 2012 Published by under Uncategorized

SASS (Syntactically Awesome Stylesheets)

Sass is a language that is interpreted into css,Basically its an extension of CSS3 which adds nested rules,variables,mixins,selector inheritance and more. it helps us to organize and maintian our css files

Compass

Compass is a framework which reads the scss files and generate css files for us.Before moving furthur,following are few things one should know, while working with Sass and Compass

Partials

partials are scss files which has to be imported to compile to a css file.usually they are named as

_(fileName).scss

However, while importing they are included with out underscore as follows

@import “fileName”

Working with Sass and Compass:

1)Install Ruby

2)Instal Ruby Gem

3)Intall sass by following command

gem install sass

4)Install compass by following command

gem install compass

5)Create a Project by following command

compass create

Following folders will be created
a)stylesheets
b)sass
and config.rb file.

sass directory is the input folder,place all yout .scss files here.
stylesheets is the output folder,all the css files are generated here

6)Compile all the scss files into css files by following command

compass watch

7)keep running the console, so that all the changes are automatically detected and css files are generated.

8)Configuring the input and output directories can be done by modifiying the config.rb file

Tip: To make the relative path to appear in the css file, edit the config.rb file and the stylesheets directory and rerun the compass watch command.

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JavaScript Concepts that every UI Engineer should be aware off

Mar 21 2012 Published by under Uncategorized

Following are some of the Javascript Concepts, Which every engineer should be aware off.

1)why Functions are called first class objects in javascript?

Explanation:

a) Functions can be assigned as a variables
b) Stored in data structures
c) Passed into functions as arguments
d) Returned from functions

 

2)What is a Closure in JavaScript ?

Explanation:

A closure is a function with access to variables in its containing scope..(the function closes over the variables).This is due to the lexical scoping. the inner function can access variables of outer function.

Example:
function attachListeners() {
for (var i = 0; i < 10; i++) {
$(‘#id-’ + i).click(
function () { alert(“I am element number ” + i); }); } }

 

There are 10 DOM elements in the page with id’s as follows “id-1″,”id-2″ …..etc. onclick of the element with “id-1″ will show the value of the i as 10 !!!!.

To solve the above issue,place the click callback in a separate function.

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jQuery Introduction

Dec 12 2011 Published by under jQuery

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jQuery’s $.animate() API ‘s drawbacks

Sep 18 2011 Published by under jQuery, Uncategorized

While working with jQuery animate() API, Following are the issues,I faced.

1) CSS ClassName cannot be added.

$.animate(className,1000);

I feel this is a biggest draw back of the animate() api. because we need to add css properties in the following tricky way,instead of adding ClassName straight away

Usage:

$(“#foo”).animate({  ”margin-left” : “40px”,  ”width” : “300px” }, 1000);

Solution:

Use the following plugin,which goes by the name as Animate to Class plugin.

http://plugins.jquery.com/project/animate-to-class

 

2)Limited CSS properties supported by $.animate() API.

Some CSS properties like “background-color,color..” cannot be used in this $.animate() API.

$.animate({“background-color”:”#b0d2f1″},1000);

This is the biggest drawback,Even though it is mentioned in the documentation.Developers mostly like to animate background-color in 50% of the use cases.

Solution

Following is the plugin,goes by the name “color” plugin has to be included,If you plan to use animate API to animate background color.

https://github.com/jquery/jquery-color

 

 

 

 

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Testing Javascript code Using Qunits (jQuery Testing Framework)

Jul 18 2011 Published by under jQuery

In My Personal Experience,If you develop a feature in Javascript, you must add Unit Test cases for your code.Having Unit Test Cases will really helpful in the following scenarios.

1)While Refactoring the code for improving the code
2)While Updating the code, To introduce an Enhancement

Comprehensively,If you are going to change your code,Unit test cases will really give you confidence,The changes added by you did not break the existing implementation.

In-Browser Testing:

Basically,In-Browser Testing Frameworks allows you to run your test cases by loading the html page in the browser.Following are some of the popular In-Browser testing frame works available

1)Qunit.js
2)jsUnit

I prefer Qunit.js,because it is very easy to integrate (doesn’t need any dependencies) and most popularly used now.If you want to start writing Unit Test cases using Qunit.js.Here is my help for you.Please Follow these steps

Step1:

Create an Html File and include the Qunit.js and Qunit.css ,Which will be used for running the test suites created via In-Browser Testing.

Example:

<script type=”text/javascript” src=”http://code.jquery.com/jquery-latest.js”></script>
<script type=”text/javascript” src=”http://code.jquery.com/qunit/git/qunit.js”></script>
<h1 id=”qunit-header”>QUnit example</h1>
<h2 id=”qunit-banner”></h2>
<h2 id=”qunit-userAgent”></h2>
<div id=”qunit-fixture”>test markup, will be hidden</div>

 

Step2:

Create javascript file, To write the unit test cases needed to test  javascript code. Include this file in your test html page .

Example:

If your javascript file name is dragdrop.js, then your new javascript test file will be dragdrop.test.js.Include both the dragdrop.js and dragdrop.test.js in the above said html file.

 

Step3:

Create a module to test a Feature / Function.In Setup and Tear down methods initialize and destroy the variables needed for testing.

 

 module(“Module Name”,
{
setup:function()
{
setup logic should be written is done here,called before each test case (test() method)
this        — – refers to the module.
this.variableName   —  to  add a variable,which can be accessed inside the test case
Add Html elements,if needed for testing
},
teardown:function()
{
clean up is done here, called after each test case execution (test()  method)
this.variableName = null  —  to remove the variables,added during the setup method
Remove Html elements added while setup
}
});

 

Step4:

Create Test Cases,To test the javascript code using assertions

Example:

Test Case: Test Case Should be written after a module

test(“Name of the test case”,
function(){
1)call the function to be tested
2)assert the results

Assertions:
equal(actualResult,expectedResult,message);
notEqual(actualResult,expectedResult,message);
}
});

 

Following is the sample code(Template), which will be useful for writing a testcase using Qunits

module(“test”,
{
setup:function(){},
teardown=function(){}
}
);

test(“Name”,function(){ equal(A,E,M); notEqual(A,E,M);
});

A — actual result
E — expected Result
M — Message

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Use document.getElementById instead of $(‘#Id’)

Jul 12 2011 Published by under jQuery

Three years back,I used prototype.js extensively. In prototype.js ‘$’ is used instead of document.getElementById(“”).But In these three years,I moved from prototype to jQuery,due to its awesomeness. I will write a separate post about “Why I love jQuery than Prototype.js”.

When I started using jQuery,Due to my Prototype.js background, I used $(‘#id’) extensively.But when i looked at the source code of jQuery,I came to know that $(‘#id’) does two things

1)It parses the selector passed inside $(‘selector’)

2)Uses the document.getElementById(‘id’) , Native DOM API supported across all the browsers

This will be costly,Because it does the costly operation of the regex parsing to identify the selector,Before using document.getElementById(). So I suggest Javascript Programmars to use document.getElementById instead of $(‘#id’) , Please take a look at the performance test made at following link

http://jsperf.com/id-vs-document-getelementbyid/20

Following are the Situations, where $(#id) API doesn’t return the element,where as document.getElementById(id) does return the element

1)If the Id contains spaces

$(‘#div id’) will not work (Even though having space in Id is not a preferred way, but if the id is generated dynamically based on some strings.this issue will arise.)

document.getElementById(div id) will return the element

2)Using remove() or any other jQuery API,if the $(”#id) does not return any element will cost you a lot.

$(‘#div id’).remove() will lead you to the drastic performance issues.

Instead Use :
var element = document.getElementById(div id);
if(element){$(element).remove();}

Please do share, If you have faced few more issues with $(‘#id’)

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jQuery.attr() Issues in jQuery 1.6

Jul 08 2011 Published by under jQuery

When I Upgraded my jQuery Version from  1.4.2 to 1.6 . Suddenly, My Custom implementation of  Table Row Reordering Via Drag n Drop Plugin , which was working before, started breaking. After a close Inspection into the issue.Issue is raised due to the API Change made by jQuery in version 1.6

Following is the big Change made by jQuery in 1.6.

jQuery introduced a method called jQuery.prop(). To segregate the API used for getting DOM properties of an element.Since ‘rowIndex’ is an table row property added by the DOM.jQuery.attr(‘rowIndex’) stopped returning the rowIndex Value.

To get the attributes value of an Html Element,Use the Following API

   $(element).attr(‘attributeName’);

The above code is equivalent to

 element.getAttribute(‘attribute’);

Following are Some of the attributes supported by the above jQuery API

1) src

2) href

3) customAttributes such as data-[customName]

……etc

To get the attribute property of an Element Provided by DOM,Use the Following API

 $(element).prop(‘propertyName’);

The above code is equivalent to

 element.propertyName;

Following are Some of the properties supported by the above jQuery API

1) rowIndex

2) checked

…etc

So Folks,Before Upgrading to any new Version of jQuery.Please Go through their Change Log.So that you can avoid the mistake i made.

 

 

 

 

 

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Bind First jQuery plugin

Jul 08 2011 Published by under jQuery, Uncategorized

While working with my co developers,I had a Following Use case

1)An Inline On Click Event Handler is attached to a button,which is created from the back-end Java Code

 <input onclick=”executeInlineFunction()” type=”button” />

2)A CallBack Function,Which has to be executed before inline Callback function on click event of the button.

Solution:

Following is the jQuery Plugin,Which helps you to add a function at the top of event handlers array

 $.fn.bindFirst = function(name, fn)
 this.bind(name, fn);    
 var handlers = this.data('events')[name.split('.')[0]];     
 var handler = handlers.pop();     
 handlers.splice(0, 0, handler); 
};

Copy the above code and below is the example to use it.

$(element).bindFirst(“click”,NthEventHandlerFunction);

$(element).bindFirst(“click”,N-1thEventHandlerFunction);

.

.

.

$(element).bindFirst(“click”,FirstEventHandlerFunction);

When the onclick event is triggerred then the event handlers are executed in the stacked order.

Here is how i have solved the problem:

I added the existing inline onclick handler into the data events and added my “customFunction” using bindFirst plugin with the following code

 

$(button).bindFirst(‘click’,$(inputelement).attr(‘onclick’));

$(button).bindFirst(‘click’,customFunction);

$(button).attr(‘onclick’) = ”;

Please share your thoughts,if you have any other solution.

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