TypeScript Boolean

Summary: in this tutorial, you will learn about the TypeScript boolean data type and how to use the boolean keyword.

Introduction to the TypeScript boolean

The TypeScript boolean type has two values: true and false. The boolean type is one of the primitive types in TypeScript.

Declaring boolean variables

In TypeScript, you can declare a boolean variable using the boolean keyword. For example:

let pending: boolean;
pending = true;
// after a while
// ..
pending = false;Code language: JavaScript (javascript)

Boolean operator

To manipulate boolean values, you use the boolean operators. TypeScript supports common boolean operators:

For example:

// NOT operator
const pending: boolean = true;
const notPending = !pending; // false
console.log(result); // false

// AND operator
const hasError: boolean = false;
const completed: boolean = true;

// OR operator
let result = completed && hasError; 
console.log(result); // false

result = completed || hasError; 
console.log(result); // trueCode language: JavaScript (javascript)

Type annotations for boolean

As seen in previous examples, you can use the boolean keyword to annotate the types for the boolean variables:

let completed: boolean = true;Code language: JavaScript (javascript)

However, TypeScript often infers types automatically, so type annotations may not be always necessary.

Like a variable, you can annotate boolean parameters or return the type of a function using the boolean keyword:

function changeStatus(status: boolean): boolean {
   //...
}Code language: JavaScript (javascript)

Boolean Type

JavaScript has the Boolean type that refers to the non-primitive boxed object. The Boolean type has the letter B in uppercase, which is different from the boolean type.

It’s a good practice to avoid using the Boolean type.

Summary

• TypeScript boolean type has two values true and false.
• Use the boolean keyword to declare boolean variables.
• Do not use Boolean type unless you have a good reason to do so.