JavaScript If Else statement

In this tutorial, you will learn about JavaScript if else statement, syntax, and create a decision-making program with the help of examples.

In the previous JavaScript tutorial, we have seen all about JavaScript for loops to execute a block of code a number of times.

In computer programming, There are many situations array where we have to execute a block of code on the basic of different-2 conditions. In such situations, you can use JavaScript if else statement that can make decisions.

In JavaScript, we have following conditional statements.

• if statement
• if…else statement
• if..else if…else statement

JavaScript if statement

JavaScript if statement is used to execute a block of code when the specified condition is true.

Syntax

if ( condition )
{
	// block of code to be executed.
	
};

Explanation:

The if statement evaluate the condition specified inside parenthesis ().

• If the condition evaluates is evaluated true, the code inside the body of if is executed.
• If the condition evaluates false, the code inside the body of if is skipped.

Flowchart of JavaScript if statement

Example: Check a number is greater than 0 or not.

// check a number if greater than 10 
num = 20;
if ( num > 10 )
{
	console.log(`${num} is greater than 10`);	
}

Output will be:- 20 is greater than 10

JavaScript if else statement

JavaScript if statement has an optional clause else, that s used to execute a block of code when the condition is false.

Syntax

if ( condition )
{
	// block of code to be executed.
}

else 
{
	// block of code to be executed
};

Explanation:

The if statement evaluate the condition specified inside parenthesis ().

• If the condition evaluates true, the code inside the body of if is executed.
• If the condition evaluates false, the code inside the body of else is executed.

Flowchart of JavaScript if..else statement

Example: Check the age of the voter.

// Check a voter can vote or not by their age.

age = prompt("Enter your exact age here:- ");
if ( age > 18 )
{
	console("You are eligible to vote");
}
else 
{
	console.log("You are not eligible to vote");
};

Output 1:-

Enter your exact age here:- 20
You are eligible to vote

Output 2:

Enter your exact age here:- 15
You are not eligible to vote

JavaScript if..else if statement

JavaScript if..else if statement is used to execute a block of code when the previous condition is false.

Syntax

if ( condition 1 )
{
	// block code 1
}

else if ( condition 2 )
{
	// block code 2

else 
{
	// block code 3
};

Explanation:

• If condition 1 is evaluated true, block code 1 is executed.
• If condition 1 is evaluated false, condition 2 is evaluated.
• If condition 2 is evaluated true, code block 2 is executed.
• If condition 2 is evaluated false, code block 3 is executed.

Flowchart of JavaScript if..else if statement

Example: Check a entered number is positive, negative or not.

number = prompt("Enter any number:- ")
if ( number > 0 )
{
	console("The Number is positive.");
	
}
else if ( number == 0 )
{

	console.log("The Number is zero.");
}
else 
{
	console.log("The Number is negative.");
};

Output 1:

Enter any number:- 10
The Number is positive.

Output 2:

Enter any number:- 0
The Number is zero.

Output 3:

Enter any number:- -10
The Number is negative.

Nested if..else statement

You can also use if..else statement inside another if..else statement, This is known as nested if..else statement.

Example:- Check a entered number is positive, negative or zero.

number = prompt("Enter any number:- ")
if ( number >= 0 )
{
	if ( number == 0 )
	{
	 
		console("Number is zero");
		
	}
	
	else 
	
	{
		console("Number is positive..");
		
	}
}
else 
{
	console.log("Number is negative");
};

Conclusion

In this tutorial, you have learned all about JavaScript if-else statements and different types of conditional statements with the help of examples. Conditional statements are very useful to execute a different-2 block of code on the basis of different-2 conditions.

Here we have seen simple examples but when you will work with real life poject, then you will perfomr more complex operations using decision making.

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