TypeScript Boolean

Introduction

In this chapter, we will explore the boolean type in TypeScript. The boolean type is used to represent logical values: true and false. Understanding how to work with booleans is essential for making decisions and controlling the flow of your TypeScript programs.

Table of Contents

• Definition
• Boolean Syntax
• Basic Operations with Booleans
• Common Boolean Methods
• Complete Example with Output
• Conclusion

Definition

In TypeScript, the boolean type is used to represent one of two values: true or false. Booleans are commonly used in conditional statements and loops to control the flow of a program.

Boolean Syntax

Syntax

let variableName: boolean = true;

Example

let isStudent: boolean = true;
let hasGraduated: boolean = false;
console.log(isStudent, hasGraduated);

Output

true false

Basic Operations with Booleans

TypeScript supports various basic operations on booleans, such as logical AND, logical OR, and logical NOT.

Example

let isStudent: boolean = true;
let hasGraduated: boolean = false;

// Logical AND
let andResult: boolean = isStudent && hasGraduated;
console.log(`Logical AND: ${andResult}`); // Output: false

// Logical OR
let orResult: boolean = isStudent || hasGraduated;
console.log(`Logical OR: ${orResult}`); // Output: true

// Logical NOT
let notResult: boolean = !isStudent;
console.log(`Logical NOT: ${notResult}`); // Output: false

Output

Logical AND: false
Logical OR: true
Logical NOT: false

Common Boolean Methods

TypeScript provides the Boolean object for working with boolean values, although it is rarely needed since most boolean operations are done using operators.

Example

let isStudent: boolean = true;
let hasGraduated: boolean = Boolean(0); // Converts 0 to false

console.log(isStudent); // Output: true
console.log(hasGraduated); // Output: false

Output

true
false

Complete Example with Output

In this section, we will combine all the examples into a single TypeScript file, compile it to JavaScript, and run it to see the output.

TypeScript Code (src/index.ts)

// Basic Boolean Operations
let isStudent: boolean = true;
let hasGraduated: boolean = false;

// Logical AND
let andResult: boolean = isStudent && hasGraduated;
console.log(`Logical AND: ${andResult}`); // Output: false

// Logical OR
let orResult: boolean = isStudent || hasGraduated;
console.log(`Logical OR: ${orResult}`); // Output: true

// Logical NOT
let notResult: boolean = !isStudent;
console.log(`Logical NOT: ${notResult}`); // Output: false

// Using Boolean Object
hasGraduated = Boolean(0); // Converts 0 to false
console.log(isStudent); // Output: true
console.log(hasGraduated); // Output: false

Compiling to JavaScript

To compile the TypeScript code to JavaScript, run the TypeScript compiler:

tsc src/index.ts

Output in JavaScript (src/index.js)

// Basic Boolean Operations
var isStudent = true;
var hasGraduated = false;

// Logical AND
var andResult = isStudent && hasGraduated;
console.log("Logical AND: " + andResult); // Output: false

// Logical OR
var orResult = isStudent || hasGraduated;
console.log("Logical OR: " + orResult); // Output: true

// Logical NOT
var notResult = !isStudent;
console.log("Logical NOT: " + notResult); // Output: false

// Using Boolean Object
hasGraduated = Boolean(0); // Converts 0 to false
console.log(isStudent); // Output: true
console.log(hasGraduated); // Output: false

Running the JavaScript

To see the output of the compiled JavaScript code, run the JavaScript file using Node.js:

node src/index.js

Conclusion

In this chapter, we covered the boolean type in TypeScript, including how to declare and use boolean variables, perform basic boolean operations, and work with the Boolean object. We provided a complete example with its output to illustrate how booleans work in TypeScript.