Augmenting the String object by extending its prototype – JavaScript

Every function in JavaScript has the prototype property which enables you to enhance the functionality of the current Object definition (the Class definition) either through adding properties or through methods. This stands true for both custom Objects as well as JavaScript defined Objects like Strings, Arrays.
Using prototypes to add functionality also has one more advantage and is performance optimized. Whatever methods or properties are defined using prototypes, they belong at the class level which means that all the instance of the Object (or rather the Class, in JavaScript there is no concept of Class, we say it Objects) will share the same copy of the method or property, rather than having their own individual copies.

In this post I am going to enhance the String Object which is already defined in JavaScript and has a lot of useful methods already available such as the split(), indexOf(), replace() etc and properties like length etc.

Now let’s add our new method to the String Object just to enhance its functionality. Let’s add a method that will remove the empty spaces between the words of a string value. For eg.

input value = The weather is very nice
output value = Theweatherisverynice

Defining our custom method
As you guessed it right we will be using the prototype property. Let’s try this thing out,

I have named our custom method as – removeEmptySpaces()

if(typeof(String.prototype.removeEmptySpaces) !== 'function'){ //you expect it to be a function if it is already there
    String.prototype.removeEmptySpaces = function(){                    
        return this.replace(/\s+/g,'');                   
    }
}

As you can see above, first we check if the removeEmptySpaces() method is already defined. If not (which is true in this case since we are adding out custom method. But the check is good to have if you do not want to overwrite a predefined method) then we define it inside the if block. So using the prototype property we add the custom method and from now on it is available to all the instances of the String Object. Inside the method definition we have a String.replace() method implemented. This will remove every occurrence of space between the words and will join them. I am using a regular expression inside the replace() method to match the spaces between the words. Once the match is found, it will be removed. You can also see the use of this keyword. This will represent the current instance that is calling our custom method – removeEmptySpaces(). 
You can learn more about the replace() method from w3schools.com

Putting it to test
Now let’s use our new method and see if it is actually doing the stuff that we wanted.

 var testStr = new String("The weather is very nice");   //create a new instance
 var newStr = testStr.removeEmptySpaces(); //call our custom method
 alert("New string after removing empty spaces is : " + newStr);

First we create a String Object instance – testStr and pass it a value. Then we call our custom method and store the returned value in newStr. Now if you alert the new value you can see that the empty spaces between the words have been removed. Here we have seen using our customized method with a String instance. What about String literals or constants? Well, we can use for them as well. Here is an example,

  var strConstant = "I am a String constant"; //defining our string literal
  var newStrConstant = strConstant.removeEmptySpaces(); 
  alert(newStrConstant); //alerts "IamaStringconstant"

So, we have seen how using prototypes we can add new functionality to our Objects. This was a simple example that I presented. You can customize any Objects as per your need.

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How to install Phonegap Facebook plugin for iOS

This post has come out of my recent struggle to integrate the Facebook Connect plugin by Dave Johnson and make it work with my Phonegap iOS app. I had a hard time figuring things out as I was new to Phonegap iOS development. I was already doing Android apps with Phonegap, but iOS has given me some tough time. Nevertheless, around 2 days of gloomy and sad face was finally rewarded with a big smile. So, better I document it somewhere so that I do not struggle again and that’s where the inspiration for this post lies. And I must say, the official documentation is pathetic for newbies.
Alright, let’s get started. I will go step by step into the process with all details and screenshots so that it is very easy for you. In this post however, I will not be talking on how to create a Phonegap iOS app, or how to create Phonegap iOS plugins. For that you still need to look at the official documentation. I will only discuss on how we can install the Facebook plugin with a Phonegap iOS app and get started using it.
Before moving further I would like to inform you that I am using Phonegap 2.2.0 for my demo. There are new versions available – 2.5.0 being the latest at the time of writing. So you might want to check the official pages if you are using the latest version of Phonegap. But the steps mentioned below should work with the new versions of Phonegap as well. OK, time to start now.

Note: Phonegap and Cordova are the same (well, at least for me..). I prefer calling Phonegap.

1) Do I need a Mac? Simple answer – Yes, you need a Mac. I have heard and read thousand times about  people asking if iOS apps can be developed in a Windows machine. Simply, I just did not research, instead I have a Mac and I started on it. But the answer is you need a Mac definitely, since you will use XCode and the iOS SDK for development.

2) Create a Phonegap iOS App – I am using Phonegap 2.2.0. I am not going to show how to create a Phonegap iOS app. For that look at this pdf documentation here. If you cannot open it, check out this link which is the pdf source. This should get you started. However I have some screenshots below which should also help you out.
a) I have created a basic Phonegap app – FacebookPluginTest inside Cordova22FacebookTest folder under Documents. See the screenshot below. I have used the Terminal to create the app. You can find details about the command in the document above. So make sure you go through it once.
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Replicating the iPhone Swipe Gesture – Vertical swiping

For those who wanted a vertical swiping feature to the the swipe gesture gallery that I created earlier, this post has a new demo and minimal explanation about a vertical swipe gesture gallery. Now you can swipe the images up or down.
I will not go through the basics once again as I have explained them in details in my previous posts. You can refer them once again in these two tutorials – post 1, post 2. Check out the demo below. Open the link in a webkit browser in either your mobile device or your computer.

Demo link: http://rialab.jbk404.site50.net/swipegesture/vertical/

Below is a screenshot of the gallery in action. You can see that the images are being moved vertically.

Screenshot of vertical swiping through images
Screenshot of vertical swiping through images

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Replicating the iPhone Swipe Gesture – auto scrolling feature

This is an update to the Replicating touch swipe gesture javascript implementation series that I have been writing for some time now and this time I have tried out the auto scrolling feature. Sometimes users may want a auto scrolling along with the normal swipe gesture feature. This post will talk about it and the changes to code that were made to make it auto scroll. First let’s check out the demo, the demo runs in both computer webkit browsers and mobile webkit browsers.

Demo link: http://rialab.jbk404.site50.net/swipegesture/auto_scrolling/

Now, let’s talk on the implementation,
First the features of this demo-

  • Auto scrolling – the gallery slides change automatically at periodical times. Based on the requirement specify whether auto scroll stops on user interaction or continues.
  • Looping – the gallery loops and is circular.
  • Direction – supports two direction – left or right. Specify which direction the gallery should auto scroll.
  • Click/Tap to URL – click or tap to open URL’s.
  • Swipe gesture – and then the touch based swipe gesture for mobiles is available as well.

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Circular swipe gesture gallery – looping through images

This is another update to the regular swipe gesture gallery that I created in two of my earlier post – post1, post2. This time I have implemented the looping feature for the images. The gallery never ends, instead you swipe it in a circular motion. So, whenever you reach the end of the list, swipe again from right to left across your device’s screen to see the first image and also when you reach the beginning of the list you swipe from left to right of your device’s screen to see the last image again. Try out the demo first and you will get a feel of it. Check out the demo in a webkit desktop browser (Chrome, Safari) or an iOS/Android device’s browser. Click on any image to open a URL as well. So, click/tap to open URL is included.

Demo link: http://rialab.jbk404.site50.net/swipegesture/circular/

An instance of the demo application – with reduced opacity and exposed images, the darker one being the one currently displayed and is inside the wrapper div.

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Replicating the iPhone Swipe Gesture – common code for mobiles and computer browsers.

This is another update for the iPhone Swipe Gesture that I have created. This is the third update to the series – Part 1 and Part 2. In case you have missed out of the earlier tutorials and detailed explanation then you can have a look at them first, before proceeding with this tutorial. What I have been able to achieve is that, I have replicated the native iPhone swipe gesture for the iPhone web-kit browser. So, throughout the series I have been able to create a HTML/JavaScript/CSS3 version of the swipe gesture. If in case, again you are not sure of the swipe gesture and swiping, I would recommend to go through my previous tutorials – Part1 and Part2.

Now, the update and the agenda of this tutorial is that – I have developed a common universal code for mobile browsers and computer browsers. Note that when I am saying browsers I mean web-kit browsers – Chrome & Safari in computers, and then the default web browsers in iOS and Android mobiles. The major changes are in the javascript code, where I have automated the user event handling process. What this means is that for mobile devices touch based events are registered and listened to and then for computer browsers mouse based events are registered and handled by the script automatically. This way there is no need to hard code touch events for mobiles and mouse events for computers. The same code works everywhere.

But, still to support different device screen sizes you will need to make changes to the CSS or the asset (images) sizes. The demo that I have worked on, I have considered the iPhone resolution – 320 x 416.

Check out the demo (same link works in mobiles and computers): http://jsphkhan.github.io/swipe_gesture_common/

An image/slide showing up in portrait mode
Common implementation for mobiles and computers

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Creating a simple stacked column chart – Flex

When I was working with Flex and Action Script 3.0 I used to do a lot of Dashboard and data visualization applications. One thing that I used to do often was a stacked column chart displaying multi dimensional data. So I thought of posting an example of creating a stacked chart out of the files deep within my Flex project folders. Let’s see the demo first and then move on to the explanation.

Demo: http://jbk404.site50.net/flex/playvideo/stackedchart.html

Stacked Column Chart
Stacked Column Chart - data visualization for three countries

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HTML5 – SVG Demographic Map Dashboard Example

The previous month I was busy with experimenting a dashboard which had choropleth/thematic maps, charts, interactivity, also dynamic data reading. Here is what I came up with. This one is a HTML5 based dashboard. Looks like a Flex application isn’t it? The map is of United States and the demographic data are just demo data although they are read from XML files. What’s good is that this application can scale, in the sense that the data can be fed to it by services running on remote servers and the map can display that. Also the data distribution has two categories a) Equal Distribution b) Quantiles method. Had to look up the statistic book again for these two. Play with the application and let me know if you like it.

The application is meant for computer browsers that support HTML5 Canvas and Inline SVG. You can best view it in Chrome, FF and Safari.

Click on the link or the image below to see the live http://jsphkhan.github.io/html5_svgmap/.


Note: The script code needs a bit of re-factoring. I am working on it partially due to time constraints. Once you have the code, you can modify it as per your needs.

FOr the source code you can grab it from the Git repo: https://github.com/jsphkhan/jsphkhan.github.io/tree/master/html5_svgmap