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Monthly Archives: March 2012


Learning experience with JavaScript is more excited day-by-day.

//
(function(undefined) {
    alert(typeof undefined);   // boolean
})(true);
//
(function(undefined) {
    alert(typeof undefined);   // undefined
})();
//

Refer jQuery source code (development version 1.7.1) and modernizr, the first line would be

\\
\\ http://code.jquery.com/jquery-1.7.1.js 
(function( window, undefined ) {

})( window );
\\ http://www.modernizr.com/downloads/modernizr.js
window.Modernizr = (function( window, document, undefined ) {

})(this, this.document);
\\

To overcome the issue of undefined, these libraries passing undefined as local variable. Notice the third parameter is left blank.

Read my another post regarding the same topic.


In Javascript subtracting a string 5 from numeric 5 is legal and it will give you the correct result !!.

But when subtracting 5 from a string “five” it will not provide you the correct answer but javascript will not throw any error either!. In fact, it will return a value !!. The value is NaN (Not a number) and its type is number!!!.

\\
alert(5-'5');      \\ 0
alert(5-'five');   \\ NaN (no errors)
alert(typeof NaN); \\ number
\\

If a number is divided by zero, javascript returns a numeric value!!! The value is infinite. Yes it is of type number!!!

\\
alert(5/0);   \\ infinity
alert(typeof infinity); \\ number
\\

So, in javascript not only 1, 2, 3, etc., are numbers but also NaN and infinite!!