MARK	GRADE
> 90	1 - OUTSTANDING
71-90	2 - EXCELLENT
51-70	3 - GOOD
41-50	4 - SATISFACTORY
< = 40	5 - POOR

CODE:
< Html >
< Head >
< Title >Program - To test witch command in JavaScript < /Title >
< /Head >
< Body >
< script language="javascript" type="text/ javascript" >
var grade=0;
var marks=prompt("Please enter your marks/100:","0' };
if(marks >90) ,
{grade = 1; }
else if(marks>70)&&(marks<=90) {grade=2;}
else if(marks>50)&&(marks<=70) {grade=3; }
else if(marks>40)&&(marks<=50) {grade=4; } .
else {grade=5; }
switch(grade)
{
case 1:
document.write("Your Grade is Outstanding ..' };
break;
case 2'
document.write("Your Grade is
Excellent..'');
break;
case 3:
document. writef'Your Grade isGood..'');
break;
case 4:
document.write("Your Grade is Satisfectory ..'');
break;
default:
document.write("Your Grade Poor and have to re-appear Exam..'');
}
< /script >
< /Body >
< /Html >

The for structure within parenthesis there are three parts each separated by semicolon.
They are:
i) The first part of the loop initialize a variable which is also called as control variable.
ii) In most case the control variable is declared as well as initialized.
iii) The second part isthe conditional statemem that determines how many times the loop will be iterated.
iv) The third and final part determines how the value of control variable is changed (Incremented/Decremented)

In JavaScript there are times when the same portion of code needs to be executed many times with slightly different values is called Loops. JavaScript supports three kinds of looping statements.
They are
for loop
while loop
do .. while loop

if (expression)
{
// Execute code block #1
}
else if (expression)
{
// Execute code block #2
}
else if (expression)
{
// Execute code block #3
}
else
{
// if all else fails, execute block #4
}

The if statement is the fundamental control statement that allows JavaScript to make decisions to execute statements conditionally. This statement has two forms. The form is for only true condition.
The syntax is
if(condition)
{
True block;
}
Types of if statement:
if else statement
else if statement
nested if statement

< html >
< head >
< title > Type casting < /title >
< /head >
< body bgcolor=orange >
< Font size = 7 >
< script language = "javascript" type = ''text! javascript ">
var x = 6 + parsent('3');
document.write (x);
< /script >
< /Font >
< /body >
< /html >

Branching Statements:
1. JavaScript supports branching statements which are used to perform different actions based on different conditions.
2. Branching is a transfer of control from the current statement to another statement or construct in the program unit.
3. A branch alters the execution sequence.

1. The switch statement begins by evaluating an expression placed between parenthesis, much likethe if statement.
2. The result compared to labels associated with case structure that follow the switch statement.
3. If the result is equal to a label, the statements in the corresponding case structure are executed.

if (expression)
{
statements if true
}
else
{
statements if false
}

1. JavaScript supports branching statements which are used to perform different actions based on different conditions.
2. Branching is a transfer of control from the current statement to another statement or construct in the program unit.
3. A branch alters the execution sequence .

while loop
In JavaScript while loop is most basic loop. The purpose of a while loop is to execute a statement / block of statement repeatedly as long as an expression is true.
The while statement creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.
The syntax is:
while (condition)
{
body of the loop
}
Example:
< Html >
< Head >
< Title >P rogram - To test while
statement in JavaScript < /Title >
< /Head >
< Body >
< script language="javascript" type="text/
javascript" >
document.write("< h2 >  Using while
Statement < /h2 >'');
var no2=0;
whlle(no2 <=5)
{
document. write( no2+" ");
no2=no2+1;
}
< /script >
< /Body >
< /Html >

To execute a while statement, the interpreter first evaluates expression. If the value of the expression is true the interpreter executes the statement and repeats, jumping back to the top of the loop and evaluating expression again. In the above example let us see how the while command is executed,
1. Initial value of the variable no2 is set to 0.
2. The expression in the while statement is executed.
3. If the condition is true then body of the loop will be executed once otherwise body of the loop will be skipped and control will jump to next statement to end of the loop.
4. Then the. value of the control variable is executed and control jumps to condition again go to step 3.

< Html >
< Body >
< script language="Javascript" type="text/ javascript" > .
var N=0;
var N = promt ("Enter the Number","0");
switch (N)
{
case 1 :
document.write ("One");
break;
case 2 :
document.write ("Two");
break;
case 3 :
document.write ("Three");
break;
case 4 :
document.write ("Four");
break;
case 5 :
document.write ("Five");
break;
default:
document.write ("Invalid! Enter between 1 and 5");
}
< /script >
< /body >
< /Html >

The do ..while loop is like a while loop, except that the loop expression is tested at the end of the loop rather than at the beginning. This means that the body of the loop is always executed a,t least once. The syntax is:
do
{
body of the loop
} while (expression);
An important difference between while and do ..
while statement is in the do ..while loop
body of the loop always executed at least once before the condition can be executed. In a while loop, first condition will be evaluated and then only based on the result of the condition the body of the loop will be executed or not.
Using do ..while loop
< Html >
< Head >
< Title >Program - To test do ..while statement in
JavaScript < /Title >
< /Head >
< Body >
< script language="javascript" type="text/ javascript" >
document.write("< h2 > Using do ..while
Statement < /h2 >");
var no2=0; do
{
document. write(no2+"");
no2=no2+2;
}while(no2< = 10);
< /script >
< /Body >
< /Html >

In JavaScript while loop is another most basic loop. The purpose of a while loop is to execute a  statement /block of statement repeatedly as long as an expression is true.
The while statement creates a loop that executes a specified statement as long as the test condition evaluates to true. The condition is evaluated before executing the statement.
The syntax is:
while (condition)
{
body of the loop
}
Using while loop:
< Html >
< Head >
< Title >Program - To test while statement in
JavaScript < /Title >
< /Head >
< Body >
< script language=;"javascript" type="text/ javascript" >
document.write("< h2 > Using while Statement < /h2 >");
var no2=0; while(no2< =5)
{
document. write(no2+"");
no2=no2+1;
}
< /script >
< /Body >
< /Html > 

To execute a" while statement, the interpreter first evaluates expression. If the value of the expression is true the interpreter executes the statement and repeats, jumping back to the top of the loop and evaluating expression again. In the above example let us see how the while command is executed,
1. Initial value of the variable no2 is set to 0
2. The expression in the while statement IS executed.
3. If the condition is true then body of the loop will be executed once otherwise body of the loop will be skipped and control will jump to next statement to end of the loop.
4. Then the value of the control variable is executed and control jumps to condition again go to step 3.