Question

How to use the Boolean object in TypeScript

Answer 1

/**
 * Boolean Example in TypeScript
 * -----------------------------
 * Demonstrates:
 * - Creating boolean variables
 * - Boolean expressions
 * - Comparison operators
 * - Logical operators
 * - Conditional statements
 * - Custom functions
 * - Type annotations
 */


/*
Key operators include:
----------------------
&& // AND
|| // OR
! // NOT
=== // Strict equality
!== // Strict inequality
*/

"use strict";

/**
 * Determines whether a user is an adult.
 *
 * @param age User's age
 * @returns True if age is 18 or older
 */
function isAdult(age: number): boolean {
    return age >= 18;
}

/**
 * Determines whether a user can log in.
 *
 * @param isActive Whether the account is active
 * @param isLocked Whether the account is locked
 * @returns True if login is allowed
 */
function canLogin(isActive: boolean, isLocked: boolean): boolean {
    return isActive && !isLocked;
}

/**
 * Converts a boolean value into a user-friendly string.
 *
 * @param value Boolean value
 * @returns "Yes" or "No"
 */
function toYesNo(value: boolean): string {
    return value ? "Yes" : "No";
}

// ----------------------------------------------------
// Boolean Variables
// ----------------------------------------------------

const isLoggedIn: boolean = true;
const isAdmin: boolean = false;

console.log("=== Boolean Variables ===");
console.log("Logged In:", isLoggedIn);
console.log("Admin:", isAdmin);

// ----------------------------------------------------
// Comparison Operators
// ----------------------------------------------------

console.log("\n=== Comparison Operators ===");

const age: number = 21;

const isOldEnough: boolean = age >= 18;
const isSenior: boolean = age >= 65;

console.log("Adult:", isOldEnough);
console.log("Senior:", isSenior);

// ----------------------------------------------------
// Equality Operators
// ----------------------------------------------------

console.log("\n=== Equality Operators ===");

const score: number = 100;

const isPerfectScore: boolean = score === 100;

console.log("Perfect Score:", isPerfectScore);

// ----------------------------------------------------
// Logical AND (&&)
// ----------------------------------------------------

console.log("\n=== Logical AND ===");

const hasUsername: boolean = true;
const hasPassword: boolean = true;

const canAuthenticate: boolean =
    hasUsername && hasPassword;

console.log("Can Authenticate:", canAuthenticate);

// ----------------------------------------------------
// Logical OR (||)
// ----------------------------------------------------

console.log("\n=== Logical OR ===");

const isManager: boolean = false;
const isSupervisor: boolean = true;

const hasAccess: boolean =
    isManager || isSupervisor;

console.log("Has Access:", hasAccess);

// ----------------------------------------------------
// Logical NOT (!)
// ----------------------------------------------------

console.log("\n=== Logical NOT ===");

const isDisabled: boolean = false;

console.log("Disabled:", isDisabled);
console.log("Enabled:", !isDisabled);

// ----------------------------------------------------
// Conditional Statements
// ----------------------------------------------------

console.log("\n=== Conditional Statement ===");

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

// ----------------------------------------------------
// Custom Function Example: isAdult
// ----------------------------------------------------

console.log("\n=== Function: isAdult ===");

const isUserAdult: boolean = isAdult(age);

console.log(`Age ${age} is adult: ${isUserAdult}`);

// ----------------------------------------------------
// Custom Function Example: canLogin
// ----------------------------------------------------

console.log("\n=== Function: canLogin ===");

const accountIsActive: boolean = true;
const accountIsLocked: boolean = false;

const loginAllowed: boolean =
    canLogin(accountIsActive, accountIsLocked);

console.log("Login Allowed:", loginAllowed);

// ----------------------------------------------------
// Ternary Operator
// ----------------------------------------------------

console.log("\n=== Ternary Operator ===");

const status: string =
    loginAllowed ? "Allowed" : "Denied";

console.log(status);

// ----------------------------------------------------
// Convert Boolean to Friendly Text
// ----------------------------------------------------

console.log("\n=== Friendly Output ===");

console.log(
    `Can Login: ${toYesNo(loginAllowed)}`
);

console.log(
    `Is Admin: ${toYesNo(isAdmin)}`
);


/*
run:

=== Boolean Variables ===
Logged In: true
Admin: false

=== Comparison Operators ===
Adult: true
Senior: false

=== Equality Operators ===
Perfect Score: true

=== Logical AND ===
Can Authenticate: true

=== Logical OR ===
Has Access: true

=== Logical NOT ===
Disabled: false
Enabled: true

=== Conditional Statement ===
Welcome back!

=== Function: isAdult ===
Age 21 is adult: true

=== Function: canLogin ===
Login Allowed: true

=== Ternary Operator ===
Allowed

=== Friendly Output ===
Can Login: Yes
Is Admin: No

*/

 

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Answer 2

/**
 * Boolean Example in TypeScript
 * -----------------------------
 */

interface User {
    username: string;
    isActive: boolean;
    isAdmin: boolean;
}

function canEditSettings(user: User): boolean {
    return user.isActive && user.isAdmin;
}

const user: User = {
    username: "Lucy",
    isActive: true,
    isAdmin: false
};

console.log(canEditSettings(user));


/*
run:

false

*/

 

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