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Boolean Data Type in JavaScript

In JavaScript, Boolean is a built-in data type that represents a logical value. It can have one of two values: true or false. The Boolean data type is used to store the result of logical operations and comparisons.


Creating Boolean Values​

You can create Boolean values in JavaScript using the true and false literals. Here are examples of both values:

Using true and false Literals​

You can create Boolean values using the true and false literals. These are case-sensitive and must be written in lowercase:

app.js
let isTrue = true;
let isFalse = false;

console.log(isTrue); // Output: true
console.log(isFalse); // Output: false

Using Logical Expressions​

You can also create Boolean values using logical expressions that evaluate to true or false. For example:

app.js
let greaterThan = 10 > 5; // true
let lessThan = 5 < 2; // false

console.log(greaterThan); // Output: true
console.log(lessThan); // Output: false

Common Operations with Boolean Values​

Logical Operators​

You can perform logical operations on Boolean values using logical operators. The following logical operators are supported in JavaScript:

  • Logical AND (&&): Returns true if both operands are true, otherwise returns false.
  • Logical OR (||): Returns true if at least one of the operands is true, otherwise returns false.
  • Logical NOT (!): Returns true if the operand is false, and false if the operand is true.
  • Logical XOR (exclusive OR) (^): Returns true if exactly one of the operands is true, otherwise returns false.

Here are examples of using logical operators with Boolean values:

app.js
let a = true;
let b = false;

console.log(a && b); // Output: false
console.log(a || b); // Output: true
console.log(!a); // Output: false
console.log(a ^ b); // Output: true

Comparison Operators​

You can compare Boolean values using comparison operators. The following comparison operators are supported in JavaScript:

  • Equal to (== or ===): Returns true if the operands are equal, otherwise returns false.
  • Not equal to (!= or !==): Returns true if the operands are not equal, otherwise returns false.
  • Greater than (>): Returns true if the left operand is greater than the right operand, otherwise returns false.
  • Less than (<): Returns true if the left operand is less than the right operand, otherwise returns false.
  • Greater than or equal to (>=): Returns true if the left operand is greater than or equal to the right operand, otherwise returns false.
  • Less than or equal to (<=): Returns true if the left operand is less than or equal to the right operand, otherwise returns false.
  • Strict equality (===): Returns true if the operands are equal and of the same type, otherwise returns false.
  • Strict inequality (!==): Returns true if the operands are not equal and/or not of the same type, otherwise returns false.
  • Logical AND (&&): Returns true if both operands are true, otherwise returns false.
  • Logical OR (||): Returns true if at least one of the operands is true, otherwise returns false.

Here are examples of using comparison operators with Boolean values:

app.js
let a = true;
let b = false;

console.log(a === b); // Output: false
console.log(a !== b); // Output: true
console.log(a > b); // Output: true
console.log(a < b); // Output: false
console.log(a >= b); // Output: true
console.log(a <= b); // Output: false

Conditional (Ternary) Operator​

You can use the conditional (ternary) operator to assign values based on a condition. The syntax of the conditional operator is as follows:

condition ? valueIfTrue : valueIfFalse;

Here's an example of using the conditional operator with Boolean values:

app.js
let a = true;
let b = false;

let result = a ? "It's true" : "It's false";
console.log(result); // Output: It's true

result = b ? "It's true" : "It's false";
console.log(result); // Output: It's false

The conditional operator evaluates the condition (a or b in this case) and returns the value specified after ? if the condition is true, and the value specified after : if the condition is false.


Converting Values to Boolean​

You can convert values to Boolean using the Boolean() function. The Boolean() function converts a value to a Boolean value based on the truthy or falsy nature of the value. Here's how it works:

  • If the value is falsy (e.g., 0, null, undefined, NaN, false, or an empty string ""), it returns false.
  • If the value is truthy (e.g., non-zero numbers, non-empty strings, objects, arrays, functions), it returns true.
  • For Boolean values, it returns the value as is.

Here are examples of converting values to Boolean using the Boolean() function:

app.js
console.log(Boolean(0)); // Output: false
console.log(Boolean(1)); // Output: true
console.log(Boolean("")); // Output: false
console.log(Boolean("Hello")); // Output: true
console.log(Boolean(null)); // Output: false
console.log(Boolean(undefined)); // Output: false
console.log(Boolean({})); // Output: true
console.log(Boolean([])); // Output: true
console.log(Boolean(function () {})); // Output: true
console.log(Boolean(true)); // Output: true
console.log(Boolean(false)); // Output: false

The Boolean() function is useful when you need to convert values to Boolean for logical operations or comparisons.


Conclusion​

In this tutorial, you learned about the Boolean data type in JavaScript, how to create Boolean values using true and false literals, and common operations with Boolean values. You also learned how to convert values to Boolean using the Boolean() function.