01_data_types.js

/**
 * The `dataTypes` function illustrates the variety of data types in JavaScript:
 * - Undefined
 * - Null
 * - Boolean
 * - Number
 * - BigInt
 * - String
 * - Symbol
 * - Object
 * - Function
 * - Array
 */

function dataTypes() {
    /**
     * ========================
     * Undefined
     * ========================
     * An "undefined" type represents a variable that has been declared but not yet
     * initialized with a value.
     */
    let undefinedVar;
    console.log(`Undefined: ${undefinedVar}, typeof: ${typeof undefinedVar}`);

    /**
     * ========================
     * Null
     * ========================
     * The "null" type signifies the intentional absence of a value.
     * Note: typeof null will return 'object', which is a longstanding bug in JavaScript.
     */
    let nullVar = null;
    console.log(`Null: ${nullVar}, typeof: ${typeof nullVar}`);

    /**
     * ========================
     * Boolean
     * ========================
     * The "boolean" type has two possible values: true or false.
     */
    let bool = true;
    console.log(`Boolean: ${bool}, typeof: ${typeof bool}`);

    /**
     * ========================
     * Number
     * ========================
     * The "number" type can represent both integers and floating-point numbers.
     */
    let num = 42;
    let float = 42.42;
    console.log(`Number: ${num}, typeof: ${typeof num}`);
    console.log(`Floating-Point Number: ${float}, typeof: ${typeof float}`);

    /**
     * ========================
     * BigInt
     * ========================
     * The "BigInt" type can represent integers of arbitrary length.
     */
    let bigInt = 42n;
    console.log(`BigInt: ${bigInt}, typeof: ${typeof bigInt}`);

    /**
     * ========================
     * String
     * ========================
     * The "string" type represents textual data.
     */
    let str = "Hello";
    console.log(`String: ${str}, typeof: ${typeof str}`);

    /**
     * ========================
     * Symbol
     * ========================
     * The "Symbol" type represents a unique value that's not equal to any other value.
     */
    let sym = Symbol("description");
    console.log(`Symbol: ${String(sym)}, typeof: ${typeof sym}`);

    /**
     * ========================
     * Object
     * ========================
     * The "object" type represents a collection of key-value pairs.
     */
    let obj = { key: "value" };
    console.log(`Object: ${JSON.stringify(obj)}, typeof: ${typeof obj}`);

    /**
     * ========================
     * Function
     * ========================
     * Functions in JavaScript are objects with the capability of being callable.
     */
    function func() {}
    console.log(`Function: ${func}, typeof: ${typeof func}`);

    /**
     * ========================
     * Array
     * ========================
     * Arrays are specialized objects used to store multiple values in a single variable.
     */
    let arr = [1, 2, 3];
    console.log(`Array: ${arr}, typeof: ${typeof arr}`);

    /**
     * ========================
     * Nuances
     * ========================
     * Null is a falsy value but it's not the boolean 'false'.
     */
    console.log(`Nuances: Null is falsy but not false: ${Boolean(nullVar) === false && nullVar !== false}`);
}

dataTypes();