Sunday, February 17, 2013

Introduction to JavaScript


JavaScript:
JavaScript is a scripting language that allows creation of interactive web pages. JavaScript allows user entries which are loaded into a HTML form to be processed as required. This feature empowers a website to return site information according to a user request.

Advantages
1.    An interpreted language
2.    Embedded with HTML
3.    Quick development and easy to learn
4.    Procedural capability:
                                      This language supports facility for checking, looping and branching.
5.    Easy debugging and testing
6.    Platform Independent

Structure of JavaScript section:
<head>
            <script language=”Text/Javascript” >
                        Code
            </script>
</head>


Data types in JavaScript:
1.    Number:
This data type consists of integer and floating point numbers and a special value NaN (Not a Number).
2.    Boolean:
It consists of the logical value either true or false.
JavaScript automatically converts the Boolean value (true/false) into one and zero when they are used in numerical expression.
3.    String:
Is consists of string values that are enclosed in single or double quotes.
For ex:
          ’Manak Nagar , Rajnagar’
          “Radhey”
4.    Null:
It consists of single value NULL which identifies an empty or non existence reference.


Some Important Points:-
1.    JavaScript is also “non case-sensitive” language.
2.    Declaration of variables in JavaScript should be in case-sensitive manner.
3.    Variable names can begin with an uppercase letter, lower case letter, an underscore character (_) or a dollar sign character ($). The remaining character can consists lower case, upper case, special symbols or digit (0-9).
4.    JavaScript does not allow the data type of the variable to be declared when a variable is created.
The same variable may be used to hold different types of data at different times with a different code snippet.


Literal:
Literals are fixed values which never change in a program.
Integer literal can be represented in JavaScript in the form of decimal/hexadecimal/octal.

Creating variable in JavaScript:
Syntax:-
          var “variable_name” = value;

Ex:
          var num=1000;
          var num=”string”;
The equal sign is used to assign a value to a variable which is known as assignment operator.

Note:
<script> tag is used to implement a script.
Language=”javascript”
Type=”text/javascript” language & type attributes are used with script tag to identify which type of scripting language is being used.


JavaScript Practice:
Program 1
<html>
            <head>
                        <script type=”text/javascript”>
                                    document.write (“Hello world”);
                        </script>
            </head>
            <body>
            </body>
</html>

If a user wants to show the text in the next line so it should use document.writeln instead of document.write.

Program 2
Write HTML Tags with javascript –
<html>
            <head>
                        <script language=”javascript”>
                                    document.write (“<h1>Hello world</h1>”);
                        </script>
            </head>
            <body>
            </body>
</html>

Program 3
Javascript in body section –
<html>
            <head>
            </head>
            <body>
                        <script type=”text/javascript”>
                                    document.write (“Hello world”);
                        </script>
            </body>
</html>

Program 4
An external Javascript –
<html>
            <head>
                        <script src=”javascript path (ex: x.js)”>
                        </script>
            </head>
            <body>
                        <script src=”javascript path (ex: y.js)”>
                        </script>
            </body>
</html>

Program 5
WAHP which use as Javascript and gives your name, contact no. And full address in different line.
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    document.write (“Name= Lucky”);
                                    document.writeln (“Contact No. = 7737873339”);
                                    document.writeln (“Address : Manak Nagar, 100 ft road,                                        Rajnagar”);
                        </script>
            </body>
</html>

Program 6
WAHP which use as Javascript and declare a variable assigning a value to it and display it
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    Var a=10;
                                    Document.writeln(“My age is : ”+a);
                        </script>
            </body>
</html>

Program 7
WAHP which use as Javascript and declare a variable assigning a value to it and display it
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    Var  name=”Govinda”
                                    Document.writeln(name);
                                    name=”Lucky”;
                                    Document.writeln(name);
                                    Document.writeln(“My name is : ”+name+”I am in III year”);
                        </script>
            </body>
</html>

Selection/Conditional Statements in JavaScript :

Program 8 ( If Statement )
WAHP which use as Javascript and use if statement
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    var day=”saturday”;
                                    if(day=”saturday”)
                                                document.write(“It is saturday”);
                        </script>
            </body>
</html>

Program 9 ( If-else Statement )
WAHP which use as Javascript and use if-else statement
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    var a=”10”;
                                    var b=”20”;
                                    if(a>b)
                                                document.write(a+“ is greater than ”+b);
                                    else
                                                document.write(b+“ is greater than ”+a);
                        </script>
            </body>
</html>

Program 10 ( Switch-case Statement )
WAHP which use as Javascript and use switch-case statement
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    var day=”5”;
                                    switch(day)
                                    {
                                      case 1:
                                                document.write(“Monday”);
                                                break;
                                      case 2:
                                                document.write(“Tuesday”);
                                                break;
                                      case 3:
                                                document.write(“Wednesday”);
                                                break;
                                      case 4:
                                                document.write(“Thursday”);
                                                break;
                                      case 5:
                                                document.write(“Friday”);
                                                break;
                                      case 6:
                                                document.write(“Saturday”);
                                                break;
                                      case 7:
                                                document.write(“Sunday”);
                                                break;
                                      default :
                                                document.write(“Not a valid day”);
                                    }
                        </script>
            </body>
</html>

Program 11 ( Immediate If)
WAHP which use as Javascript and use Immediate if (Conditional operator/Ternary operator)
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                                    var day=”saturday”;
                                    (day==”saturday”)?document.write(“Weekend”)­:document.write(“Not Weekend”);
                        </script>
            </body>
</html>

Loop in JavaScript :

Program 12 ( For Loop)
WAHP which use as Javascript and use for loop
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                        var n;
                        for(n=1;n<=10;n++)
                        {
                          Document.writeln(“value is : ”+n);
                        }
                        </script>
            </body>
</html>


Program 13 (While Loop)
WAHP which use as Javascript and use While loop
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                        var n;
                        n=1;
                        while(n<=10)
                        {
                          Document.writeln(“value is : ”+n);
                          n++;
                        }
                        </script>
            </body>
</html>


Program 14 (Do-While Loop)
WAHP which use as Javascript and use Do-While loop
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                        var n;
                        n=1;
                        do
                        {
                          Document.writeln(“value is : ”+n);
                          n++;
                        }while(n<=10);
                        </script>
            </body>
</html>


Program 15
WAHP which use as Javascript and prints a table
<html>
            <head>
            </head>
            <body>
                        <script language=”javascript”>
                        var n=2;
                        var i,t;
                        for(i=1;i<=10;i++)
                        {
                          t=n*i;
                          Document.writeln(n + “ X ”+ i +” = “ + t);
                        }
                        </script>
            </body>
</html>


1 comment:

Powered by Blogger.