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JavaScript if, else, and else if

Conditional Statements

While writing the code, if you want certain actions to be performed actions for different decisions; you can use conditional statements.

In JavaScript we have the following conditional statements:

  • Use if to define a block of code to be executed, if a mentioned condition is true.
  • Use else to define a block of code to be executed if the same condition is false
  • Use else if to define a new condition to test, if the first condition is false.
  • Use switch to define many alternative blocks of code to be executed.

The if Statement

Use the if statement to define a block of JavaScript code to be executed if a condition is true.

Syntax

if (condition) {

  //  block of code to be executed if the condition is true

}

Example

Make a “Good day” greeting if the hour is less than 18:00:

<!DOCTYPE html>

<html>

<body>

<h2>JavaScript if</h2>

<p>Display “Good day!” if the hour is less than 18:00:</p>

<p id=”demo”>Good Evening!</p>

<script>

if (new Date().getHours() < 18) {

 document.getElementById(“demo”).innerHTML = “Good day!”;

}

</script>

</body>

</html>

Output

JavaScript if

Display "Good day!" if the hour is less than 18:00:

Good Evening!

The else Statement

Use the else statement to define a block of code to be executed if the condition is false.

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

}

Example

If the hour is less than 18, create a “Good day” greeting, otherwise “Good evening”:

<!DOCTYPE html>

<html>

<body>

<h2>JavaScript if .. else</h2>

<p>A time-based greeting:</p>

<p id=”demo”></p>

<script>

const hour = new Date().getHours();

let greeting;

if (hour < 18) {

  greeting = “Good day”;

} else {

  greeting = “Good evening”;

}

document.getElementById(“demo”).innerHTML = greeting;

</script>

</body>

</html>

Output

JavaScript if .. else

A time-based greeting:

Good day

The else if Statement

Use the else if statement to define 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

}

Example

If time is less than 10:00, create a “Good morning” greeting, if not, but time is less than 20:00, create a “Good day” greeting, otherwise a “Good evening”:

<!DOCTYPE html>

<html>

<body>

<h2>JavaScript if .. else</h2>

<p>A time-based greeting:</p>

<p id=”demo”></p>

<script>

const time = new Date().getHours();

let greeting;

if (time < 10) {

  greeting = “Good morning”;

} else if (time < 20) {

  greeting = “Good day”;

} else {

  greeting = “Good evening”;

}

document.getElementById(“demo”).innerHTML = greeting;

</script>

</body>

</html>

Output

JavaScript if .. else

A time-based greeting:

Good day


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