Learning Objective: Understand what Booleans are, and how to use them to add basic logic to your programs.

What Are Booleans?

A Boolean is a data type that can only have one of two values:

• — meaning “yes,” “correct,” or “on.”
• — meaning “no,” “incorrect,” or “off.”

Booleans are essential for decision-making in programming. They help control the flow of your program, allowing it to act differently depending on conditions.

Examples of Booleans

1. Assigning Booleans

You can directly assign or to variables:

const isRaining = true;
const isWeekend = false;

2. Using Booleans in Conditions

Booleans are often used in statements to decide what code to execute:

const isRaining = true;

if (isRaining) {
  console.log("Take an umbrella!");
} else {
  console.log("Enjoy the sunshine!");
}

Booleans in the Real World

Booleans also play a key role in user interactions. For example:

const isLoggedIn = false;

if (isLoggedIn) {
  console.log("Welcome back!");
} else {
  console.log("Please log in.");
}

What About Comparisons?

Boolean values often come from comparisons. For instance:

const age = 20;
console.log(age >= 18); // true

Comparisons return or , making them Booleans. We’ll dive into comparisons and logical operators in the Operators and Equality module.

Interactive Activity

1. Open VS Code and create a file called .
2. Declare Boolean variables for:
   • Whether it’s your birthday today.
   • Whether you’ve completed today’s lesson.
3. Write an statement for each Boolean:
   • Display a birthday greeting if .
   • Congratulate yourself for finishing the lesson if .

Example:

const isBirthday = false;
const completedLesson = true;

if (isBirthday) {
  console.log("Happy Birthday!");
}

if (completedLesson) {
  console.log("Great job on completing today's lesson!");
}

1. Experiment with reassigning the Booleans to see how the program reacts.

What’s Next?

In this lesson, you’ve learned how to use Booleans to control the flow of your program. Next, we’ll dive deeper into comparisons, logical operators, and how to combine multiple conditions in the Operators and Equality module.

Now, let’s dive into Null and Undefined!

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