Lazy Evaluation

var boolV = true || false || true || false || true;
 console.log(boolV); //output is true

Question is did all the operations (logical) got executed ?
Ans is NO.

If several logical operations one after the other, but the result becomes clear at some point before the end of entire operation, then the remaining operations are not performed.

Lets consider the above statement.

var boolV = true || false || true || false || true;

It is before the first local operation it is clear that boolV is  suppose to have value true irrespective of any logical or operation. hence the other logical operations are not executed. in the above statement.

To verify this, we will the following code.

var a =10;
console.log(a); //output 10
console.log(!!++a); //output true
console.log(a);        //output 11
var boolV = true || false || true || false || true || !!++a;
console.log(boolV);  //output true
console.log(a);         //output 11 (which imples the !!++a didn't got executed)
boolV =  !!++a || true || false || true || false || true ;
console.log(boolV); //output true
console.log(a);        //output 12 (which imples the !!++a  got executed)


Ain't that interesting !!!

Starting reading Object Oriented Javascript by Stoyan Stefanov again

Starting reading Object Oriented Javascript by Stoyan Stefanov again.

I used to read this book managing between my office work and completing house hold choir.
Interestingly this time, I am being asked to complete this book by tomorrow (thats a big task) and that too as an work which I'm liking it.

This book contains conceptual treasures of javascript and everytime I read, I am starting to like it more.

Small interesting codes for all.

var a=10;
var b =20;
var c = "20";

var d,e,f,g;

d= a+b;
e= a+c;
f= b+a;
g= c+a;

console.log(d);
console.log(e);
console.log(f);
console.log(g);

Can you guess the output???
d>>> 30
e>>>  1020
f>>> 30
g>>> 2010

the value of d and f remains same whereas e and f are different. since e and f becomes string variable  from the operation  e= a+c; and g= c+a;

<< number >> + << string >> will result in string concatenation
and result type will also be << string >>.

HTML5 & Detection Techniques

New Logo of  HTML5

HTML5 is the new specification of HTML 5 with lots of new feature and it is still being drafted the latest specification can be found at http://dev.w3.org/html5/spec/Overview.html .

Some of the new features are

• Numerous new tags like (article, aside, bdo, command, datalist, details, embed, footer, hgroup, keygen, mark, meter, nav, output, progress, rp, rt, ruby, section, source, summary, time, wbr). 
• Custom tag for audio and video
• Custom tags for images and its captions (figure, figcation)
• Custom tag for Custom Graphics (canvas)
• New controls for webforms like (dates, times, email, url, search, number, range, tel, color).
• Geolocation Support.
• Web Sockets: Socket programming for client browser.
• New logo to identify  HTML5.

The are lots of more features in it, I am yet to go through all of them and the draft is still being updated.

Canvas element allows dynamic and scriptable rendering of 2D shapes and bitmap images. [Read More...]

SVG (scalable vector graphics is supported using canvas element). Various representation of reports are presented using graphs, pie charts, etc. canvas element with the help of SVG allows to create nice images and graphics. Javascript is required to program the SVG in canvas element.

How can I detect if the browser is supporting HTML5?

Here we have to depend on javascript. A javascript library named Modernizr available under Open Source for HTML5 and CSS3.

However, as per Mark Pilgrim('s book HTML5 Up and Running), we can employ the following simple techniques to quickly identify HTML5 compatible browser.

1. Checking the presence of certain property on the global object(such as navigator or window object).
• Example. checking the presence of Geolocation support.
• function supports_geolocation() {
        return !!navigator.geolocation;
  }
2. After creating an element dynamically, then testing the presence of a certain property to that element.
• Example. checking the canvas support.
• function supports_canvas() {
        return !!document.createElement('canvas').getContext;
  }
3. After creating an element dynamically, then testing the presence of a certain method to that element. Then call the method if present  and check the value returned.
• Example. checking the video support.
• 
  function supports_h264_baseline_video() {
        // checks the video support
        if (!!!document.createElement('video').canPlayType;) { return false; }
        var v = document.createElement("video"); //create element
        return v.canPlayType('video/mp4; codecs="avc1.42E01E, mp4a.40.2"');
  }
4. After creating an element dynamically, set value to a property and then to test if it has retained the value.
• Example: Create a element 'input' dynamically (which is of type 'text' as default). Then setting the property 'type' to other value and retesting the value of the property 'type' 
• function supports_PropertyPersistance() {
     var i = document.createElement("input"); //default element is text
      i.setAttribute("type", "color");
      return i.type !== "text";
  }

Read More on detection technique...

Reference: http://en.wikipedia.org/wiki/HTML5
Specification - Working Draft: http://dev.w3.org/html5/spec/Overview.html
Specification - Released Working Draft: http://www.w3.org/TR/html5/

Rule of Thumb : Declaring variables

"var" is the keyword used for declaring a variable. It lets you define an number, string , datetime value or an object or function.


Example(s):

var a1;
var a2 = 10;
var a3 = 1.23;
var a4 = "hello world";
var a5 = true;
var a6 = {prop1:'some values', prop2: 'some other values', prop3 : true} ;


var a7 = new Object();
var fn1 = function() { return "hello world"};

what happens if we use in the following way

 ax=10;

Well well, the above line adds a variable name "ax" in the global scope. At a glance it can pretend to be an trivial mistake, but that is not the case, rather it is of very high importance, since such statement can make the global scope dirty and making the code fault prone and fragile.

Lets take another example for more clarity:

function sayHello(username){
  strn = "Hello " + username;
  return strn;
};


console.log( sayHello( 'kris' ) );
console.log( strn ); //=> "hello kris"

*console is a class available in almost all browsers but not in all browser for development/debugging purpose.

The above javascript function "sayHello" adds a variable "strn" to the global scope.

The following change of declaring the variable with "var" will make sure that the variable "strn" is applicable to local scope only.

Examples: 

function sayHello(username){

  var strn = "Hello " + username;

  return strn;

};

console.log( sayHello( 'kris' ) );

console.log( strn ); //=> undefined

Hence the scope of  local variable is managed correctly.

So we conclude this post with the memoirs of golden rule of variable declaration in javascript.

Beginning Javascript

The blog of mine is making a focus shift from blogging to javascript preaching.

JavaScript was earlier called "LiveScript".
you will get a good information on javascript history here wikipedia:javascript

My inception of javascript was like simple validations for web pages in 2005. Beginning 2007, I understood that javascript has some more potential. Errie, whats the potential. Well well, you can use javascript as a full blown applications. During june-2008 I wrote my first javascript class. Yessss my first javascript class.

well here it goes.

Code:

var A= function(){
  this.sayHello = function(){
    alert('hello world');
  };
};
var o = new A();
o.sayHello();

Yes it is as simple as written here.

More is on way to you.

ExtJS new version

Exciting new Sencha (EXTJS version4) has arrived.

Sencha is formerly known as EXTJS(EXTended JavaScript).

The interesting question is "So what exciting about it????"

The following are to name a few.

Using a swf runtime super cool "Drawing & Charts" exploiting the advantaqge to positioning the SWF component inside DOM using javascript with possibility to pass parameters. Its capability is not restricted rather increased with the ability of scalable vector drawing.

The Ext.Data package has been overhauled with interesting additions.

Its not last but the UI which matters the most is now supported by CSS3 themes, and the theme has been overhauled to give more richness with reduced size on browser.

Last but not the lease the "Performance" aspect has been improved drastically.
The reduced size load at DOM(i.e. DOM reduction) with an implied and tuned effect on speed gains. And the most interesting is the Infinite Scroll on Grids with data request on demand to scroll.

Click [here] to check out the beta4 version of Sencha .

Double Trouble with Keyless Entry for car

Morning was as usual good when I woke up.
Today was the first business day of the week since yesterday was holiday declared for muhharam. So you can make out that its an important day at office and that too after a 4 day long holidays.

I pressed the remote of my car. "No sound" !!
Again I pressed the unlock button. It didn't worked!!!
I tried again couple of times. All effort gone to waste.

I asked mom to get me the 2nd set of remote keys.
Tried with the 2nd set as well. But alas there was no response.

The wrist watch was pointing it to 8:46am. I was getting late.
So thought to get a forced entry by using the metal key.

Opened the lock and door.
Christ!!!
I realized what mistake I did. It started to beep like anything. It was all chaotic. Entire neighborhood turned to check out what happened.

Holy Christ!!!
The embarrassing moments. The sound was just not stoppable. It paused for 2 seconds started again. I guess it continued for 5 mins and then stopped.

The embarrassing troubled moment was over I thought. I was terribly mistaken which in a short while i came to know.

I used the key for ignition. No response!!!!!
Again i tried. No response!!!!!
Repeated couple of times again before I realized that the keyless entry mechanism had disconnected the ignition channel.

And with every ignition try the vehicle started making beeping sound like madness.

I realized the vehicle cannot be started without third party/service engineer's help.

I kept the car in garage and closed everything. Without delay headed with laptop, office document/papers and lunch box towards nearest taxi stand(cab terminal). It was already 9:10am by that time.

Thats the beginning of the day. lets see whats there kept more during the day.

Called up Maruti and the provider of the keyless entry system.
The service engineer came around 11:30 am.Thanks to Dad who was there at home to guide the service engineer.

Seems, he has replaced the main keyless entry machine.

After reaching home I'll come to know whats the status.

Advice for all:
If you car buzzer begins to beep without any notice or/and creates issues with the keyless remote, immediately take the matter to the provider.

The mentioned were the symptoms for keyless entry machine problems.

Luckily i was not out for a long drive during that period. Else god knows what more problem would have been there.