TypeScript Booleans: The Foundation of Logic

Understand the boolean data type in TypeScript: its role, declaration, and usage in conditional statements and logical operations. Learn how to effectively employ booleans to control program flow and make informed decisions.

TypeScript Boolean Data Type

Understanding Boolean Values in TypeScript

The boolean data type in TypeScript represents logical values, specifically true and false. It's fundamental for conditional statements, logical operations, and controlling program flow.

Declaration

let isPresent: boolean = true;

Key Points

• Primitive Type: boolean is a primitive data type, meaning it directly holds the value itself.
• Two Values: The only possible values for a boolean variable are true and false.
• Type Safety: TypeScript ensures that boolean variables can only hold boolean values, preventing type-related errors.

Avoiding Boolean Object

While JavaScript has a Boolean object, it's generally recommended to avoid using it in TypeScript due to potential type-related issues. The lower-case boolean is the preferred primitive type.

Incorrect:

function checkExistence(b: Boolean): void {
  // ...
}

Correct:

function checkExistence(b: boolean): void {
  // ...
}

Boolean Operations

TypeScript supports standard boolean operators:

• Logical AND (&&)
• Logical OR (||)
• Logical NOT (!)

Example:

let isLoggedIn: boolean = true;
let hasPermission: boolean = false;

if (isLoggedIn && hasPermission) {
  console.log("User is logged in and has permission.");
}

Boolean in Conditional Statements

Boolean values are essential for controlling program flow using conditional statements like if, else if, else, and switch.

Example:

let isAdult: boolean = true;

if (isAdult) {
  console.log("You are an adult.");
} else {
  console.log("You are a minor.");
}

Conclusion

The boolean data type is a cornerstone of TypeScript programming, enabling you to create logical expressions and control program flow effectively. By understanding its usage and avoiding the Boolean object, you can write cleaner and more type-safe code.