Conditional Statements In JavaScript

Introduction

In the previous chapter, we learned about Operators in JavaScript, types of operators, and how to use operators in JavaScript with example programs.

In this chapter, we will learn about Conditional Statements in JavaScript. These statements are also called Selection Statements.

The Conditional Statements in JavaScript:

If Statement
If Else Statement
Elseif Statement
Switch Case Statement

If Statement

If Statements are used for the purpose of decision making; they evaluate the statement if the condition is true. To check if the given 'If condition' is satisfied, 'If Statement' is executed; otherwise the condition is false to exit the If condition.

Syntax

If (condition)
{
Statement; //given condition is true execute the statement
}

Example

<!DOCTYPE html>
<html>
<head>
<title>if Condition</title>
</head>
<body>
<h1>Conditional Statement in JavaScript</h1>
<script type="text/javascript">
var percentage =(prompt("Enter Your Mark"))
if (percentage >= 40)
{
document.write("You Mark is Pass"); //given condition is true execute the statement
}
</script>
</body>
</html>

Output

If else Statement

'If else Statement' is an improvement over if Statement. It evaluates the statement if the condition is true or false. In this statement, the given 'If condition' is true means to execute the 'if Statement'. On the other hand, if the condition is false it means to execute another block.

Syntax

if (Condition)
{
Statement; //true
}
else
{
Statement; //false
}

Example

<!DOCTYPE html>
<html>
<head>
<title>if Condition</title>
</head>
<body>
<h1>Conditional Statement in JavaScript</h1>
<script type="text/javascript">
var percentage =(prompt("Enter Your Mark"))
if (percentage >= 40)
{
document.write("You Mark is Pass"); //given condition is true execute the statement
}
else
{
document.write("You Mark is Fail"); //given condition is false execute the statement
}
</script>
</body>
</html>

Output

Else If Statement

It is another decision-making statement. It evaluates the Statement only 'if condition' is true from several conditions, 'elseif statement' can be used many times in a program; if the two conditions are false it means else Statement is executed.

Syntax

If (condition 1)
{
statement 1; //true
}
elseif (condition 2)
{
statement 2; //true
}
else
{
statement; //evaluate if condition is false
}

Example

<!DOCTYPE html>
<html>
<head>
<title>if Condition</title>
</head>
<body>
<h1>Conditional Statement in JavaScript</h1>
<script type="text/javascript">
var mark =(prompt("Enter Your Mark"))
if (mark>= 90 && mark <=100)
{
document.write("A Grade"); //given condition is true execute the statement
}
else if (mark >= 80 && mark <=89)
{
document.write("B Grade"); //given condition is true execute the statement
}
else if (mark >= 70 && mark <= 79)
{
document.write("C Grade"); //given condition is true execute the statement
}
else if (mark >= 60 && mark <= 69)
{
document.write("D Grade"); //given condition is true execute the statement
}
else if (mark >= 35 && mark <= 59)
{
document.write("E Grade"); //given condition is true execute the statement
}
else
{
document.write("Fail"); //given condition is false execute the statement
}
</script>
</body>
</html>

Output

Below 35 mark

Switch Case

Switch Case Statement is a control Statement, it is better than If else statements. To improve the readability of a program multiple if-else Statements can be replaced with Switch Statements. In Switch Case Statements, using the break statement will cause an immediate exit from the switch statement as soon as the code under the code is executed.

Syntax