What Is JavaScript if-else Statement And How To Use It

Posted by TotalDC

JavaScript if-else statements are used to decide the flow of execution based on different conditions. If a condition is true, you can perform one action and if the condition is false, you can perform another action.

learn about javascript if-else statatements

In this article you will learn:

if statement
else-if statement
if…else if… else statement

JavaScript If Statement

Syntax:

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

You can use If statement if you want to check only a specific condition.

Try this yourself:

<head>
	<title>IF Statments</title>
	<script type="text/javascript">
		const age = prompt("Please enter your age");
		if(age>=18){
		   console.log("You are an adult <br />");
                }
		if(age<18){
		   console.log("You are NOT an adult <br />");
                }
	</script>
</head>
<body>
</body>
</html>

JavaScript If… Else Statement

Syntax:

if (condition)
{
lines of code to be executed if the condition is true
}
else
{
lines of code to be executed if the condition is false
}

You can use If….Else statement if you have to check two conditions and execute a different set of codes.

Try this yourself:

<html>
<head>
	<title>If...Else Statments</title>
	<script type="text/javascript">
		// Get the current hours
		let hours = new Date().getHours();
		if(hours<12){
		   console.log("Good Morning<br />");
                }
		else {
		   console.log("Good Afternoon<br />");
                }
	</script>
</head>
<body>
</body>
</html>

JavaScript If… Else if … Else Statement

Syntax:

if (condition1)
{
lines of code to be executed if condition1 is true
}
else if(condition2)
{
lines of code to be executed if condition2 is true
}
else
{
lines of code to be executed if condition1 is false and condition2 is false
}

You can use If….Else If….Else statement if you want to check more than two conditions.

Try this yourself:

<html>
<head>
	<script type="text/javascript">
		let one = prompt("Enter the first number");
		let two = prompt("Enter the second number");
		one = parseInt(one);
		two = parseInt(two);
		if (one == two){
			   console.log(one + " is equal to " + two + ".");
                           }
		else if (one<two){
			   console.log(one + " is less than " + two + ".");
                           }
		else {
			console.log(one + " is greater than " + two + ".");
                     }
	</script>
</head>
<body>
</body>
</html>