Boolean Values in JavaScript — Truthy and Falsy Values

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Description

In this article, we will explore Boolean values in JavaScript in detail: how they work, which values are considered truthy or falsy, and how to use them effectively in programming.

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Core Content

What is a Boolean?

The Boolean type in JavaScript has only two possible values:

• true
• false

These two values are used in conditional statements, loops, and other logical operations.

    const isLoggedIn = true;
    const hasAccess = false;

Truthy vs Falsy Values

In JavaScript, certain values are automatically converted to Booleans when required. These values are called "truthy" or "falsy".

Falsy Values

These values are considered equivalent to false in Boolean contexts:

    // These values are falsy:
    false
    0
    -0
    0n // BigInt zero
    "" // empty string
    null
    undefined
    NaN

Example:

    if (!0) {
      console.log("0 is falsy");
    }

Truthy Values

All other values are considered truthy, meaning they evaluate to true.

    // Examples:
    "Hello"
    42
    []
    {}
    function () {}

    if ("hello") {
      console.log("Strings are truthy");
    }

The Boolean() Function

You can explicitly convert a value to a Boolean using the Boolean() function.

    Boolean(0); // false
    Boolean("text"); // true

Or use the shorthand:

    !!value // Double NOT operator to coerce to Boolean

    console.log(!!"abc"); // true
    console.log(!!null);  // false

Where Are Booleans Used?

• In conditions for if, else if, while, for
• Building logical expressions
• Interacting with APIs
• Conditional rendering of components