JAVA-SCRIPT STATEMENTS

Concept:
 The  if statement specifies a block of code to be executed if a condition is true:
Syntax:

if (condition) {
    block of code to be executed if the condition is true
}

(1)if example:

<html>
   <body>
     
      <script type="text/javascript">
        
            var age = 20;
        
            if( age > 18 ){
               document.write("<b>Qualifies for driving</b>");
            }
     
      </script>
     
     
   </body>
</html>


Concept:
The else statement specifies a block of code to be executed if the condition is false:
Syntax:

if (condition) {
    block of code to be executed if the condition is true
} else { 
    block of code to be executed if the condition is false
}
(2)if else example:

<html>
   <body>
  
      <script type="text/javascript">
        
            var age = 20;
        
            if( age > 18 ){
               document.write("<b>Qualifies for driving</b>");
            }
           
            else{
               document.write("<b>Does not qualify for driving</b>");
            }
        
      </script>
      </body>
</html>

Concept:
The else if statement specifies a new condition if the first condition is false:
Syntax:
if (condition1) {
    block of code to be executed if condition1 is true
} else if (condition2) {
    block of code to be executed if the condition1 is false and condition2 is true
} else {
    block of code to be executed if the condition1 is false and condition2 is false
means no codition is matched.
}



(3)else if example :

<html>
   <body>
   <script type="text/javascript">
        
            var book ="history";
            if( book == "history" ){
               document.write("<b>History Book</b>");
            }
        
            else if( book == "maths" ){
               document.write("<b>Maths Book</b>");
            }
        
            else if( book == "economics" ){
               document.write("<b>Economics Book</b>");
            }
        
            Else
            {
               document.write("<b>Unknown Book</b>");
            }
        
      </script>
 </body>
<html>


Use the switch statement to select one of many blocks of code to be executed.
Concept:
This is how it works:
  • The switch expression is evaluated once.
  • The value of the expression is compared with the values of each case.
  • If there is a match, the associated block of code is executed.
·        Break   keyword, it breaks out of the switch block.
·        This will stop the execution of more code and case testing inside the block.
·        When a match is found, and the job is done, it's time for a break. There is no need for more testing.
·        The default keyword specifies the code to run if there is no case match


Syntax:
switch(expression) 
{
    case n1:
        code block to be executed if case n1 is matched.
        break;
    case n2:
       code block to be executed if case n2 is matched.
        break;
    default:
        default code block to be execute if no case matched 
        break;
}



(15)switch  example :

<html>
   <body>
  
      <script type="text/javascript">
        
            var grade='B';
            document.write("Entering switch block<br />");
            switch (grade)
            {
               case 'A': document.write("Good job<br />");
               break;
           
               case 'B': document.write("Pretty good<br />");
               break;
           
               case 'C': document.write("Passed<br />");
               break;
           
               case 'D': document.write("Not so good<br />");
               break;
           
               case 'F': document.write("Failed<br />");
               break;
           
               default:  document.write("Unknown grade<br />");
                                                   break;
            }
                                               
</script>
 </body>
</html>
========================================================================
JAVASCRIPT    EXAMPLE   :

<script type="text/javascript">
$a=90;
if($a>=75&&$a<=85)
{
document.write("B grade");
}
else if($a>=85 && $a<=100)
{
document.write("A grade");
}
else if($a>35 && $a<75)
{
document.write("C Grade");
}
else if($a<35)
{
document.write("fail");
}
else
{
document.write("not match");
}
</script>

output:

A grade
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