Javascript Tutorial

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  • Topic: C, Perl, JavaScript
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  • Published : January 26, 2013
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Javascript Tutorial
Javascript is a scripting language produced by Netscape for use within HTML Web pages. JavaScript is loosely based on Java and it is built into all the major modern browsers. This tutorial gives an initial push to start you with Javascript. For more detail kindly check

What is JavaScript ?
JavaScript is:

    

JavaScript is a lightweight, interpreted programming language Designed for creating network-centric applications Complementary to and integrated with Java Complementary to and integrated with HTML Open and cross-platform

JavaScript Syntax:
A JavaScript consists of JavaScript statements that are placed within the ... HTML tags in a web page. You can place the tag containing your JavaScript anywhere within you web page but it is preferred way to keep it within the tags. The tag alert the browser program to begin interpreting all the text between these tags as a script. So simple syntax of your JavaScript will be as follows

JavaScript code
The script tag takes two important attributes:

 

language: This attribute specifies what scripting language you are using. Typically, its value will be javascript. Although recent versions of HTML (and XHTML, its successor) have phased out the use of this attribute. type: This attribute is what is now recommended to indicate the scripting language in use and its value should be set to "text/javascript".

So your JavaScript segment will look like:

JavaScript code

Your First JavaScript Script:
Let us write our class example to print out "Hello World".


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Above code will display following result:

Hello World!

Whitespace and Line Breaks:
JavaScript ignores spaces, tabs, and newlines that appear in JavaScript programs. Because you can use spaces, tabs, and newlines freely in your program so you are free to format and indent your programs in a neat and consistent way that makes the code easy to read and understand.

Semicolons are Optional:
Simple statements in JavaScript are generally followed by a semicolon character, just as they are in C, C++, and Java. JavaScript, however, allows you to omit this semicolon if your statements are each placed on a separate line. For example, the following code could be written without semicolons

But when formatted in a single line as follows, the semicolons are required:

Note: It is a good programming practice to use semicolons.

Case Sensitivity:
JavaScript is a case-sensitive language. This means that language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters. So identifiers Time, TIme and TIME will have different meanings in JavaScript. NOTE: Care should be taken while writing your variable and function names in JavaScript.


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Comments in JavaScript:
JavaScript supports both C-style and C++-style comments, Thus:

   

Any text between a // and the end of a line is treated as a comment and is ignored by JavaScript. Any text between the characters /* and */ is treated as a comment. This may span multiple lines. JavaScript also recognizes the HTML comment opening sequence is not recognized by JavaScript so it should be written as //-->.

JavaScript Placement in HTML File:
There is a flexibility given to include JavaScript code anywhere in an HTML document. But there are following most preferred ways to include JavaScript in your HTML file.

   

Script Script Script Script

in in in in

... section. ... section. ... and ... sections. and external file and then include in ... section.

JavaScript DataTypes:
JavaScript allows you to work with three primitive data types:

  

Numbers eg. 123, 120.50 etc. Strings of text e.g. "This text string" etc. Boolean e.g....
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