/**
 * Checks if the given variable is a string.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is a string, false otherwise.
 */
declare const isString: (variable: unknown) => boolean;
/**
 * Checks if the given variable is not a string.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is not a string, false otherwise.
 */
declare const isNotString: (variable: unknown) => boolean;
/**
 * Checks if the given variable is a number.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is a number, false otherwise.
 */
declare const isNumber: (variable: unknown) => boolean;
/**
 * Checks if the given variable is not a number.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is not a number, false otherwise.
 */
declare const isNotNumber: (variable: unknown) => boolean;
/**
 * Checks if the given variable is a boolean.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is a boolean, false otherwise.
 */
declare const isBoolean: (variable: unknown) => boolean;
/**
 * Checks if the given variable is not a boolean.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is not a boolean, false otherwise.
 */
declare const isNotBoolean: (variable: unknown) => boolean;
/**
 * Checks if the given variable is undefined.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is undefined, false otherwise.
 */
declare const isUndefined: (variable: unknown) => boolean;
/**
 * Checks if the given variable is not undefined.
 *
 * @param {unknown} variable - The variable to check.
 * @returns {boolean} True if the variable is not undefined, false otherwise.
 */
declare const isNotUndefined: (variable: unknown) => boolean;
/**
 * Checks if a given value is a plain object.
 *
 * A plain object is an object created by the `{}` syntax, `Object.create(null)`,
 * or using `new Object()`. This function ensures that the value is an object
 * and does not have an unusual prototype chain.
 *
 * @param {unknown} value - The value to check.
 * @returns {boolean} `true` if the value is a plain object, otherwise `false`.
 *
 * @example
 * ```ts
 * console.log(isObjectStrict({})); // Output: true
 * console.log(isObjectStrict(Object.create(null))); // Output: true
 * console.log(isObjectStrict([])); // Output: false
 * console.log(isObjectStrict(new Date())); // Output: false
 * console.log(isObjectStrict(null)); // Output: false
 * ```
 *
 * **Features**
 * - ✅ Recognizes only **plain objects** (created via `{}`, `new Object()`, `Object.create(null)`, etc.).
 * - ❌ Rejects **arrays**, **functions**, **DOM elements**, **class instances**, and **custom objects** with modified constructors.
 *
 * **Behavior**
 * - ✅ `isObjectStrict({})` → `true`
 * - ❌ `isObjectStrict([])` → `false`
 * - ❌ `isObjectStrict(() => {})` → `false`
 * - ✅ `isObjectStrict(Object.create(null))` → `true`
 *
 * **When to use**
 * - Use `isObjectStrict` when you need a **strict check for plain objects**.
 * - Use `isObjectLoose` if you need to check if a value is an **object-like structure**, including functions.
 */
declare const isObjectStrict: (value: unknown) => boolean;
/**
 * Checks if a given value is an object or a function.
 *
 * This function verifies whether the provided value is of type `'object'` or `'function'`
 * while ensuring that `null` is excluded.
 *
 * @param {unknown} value - The value to check.
 * @returns {boolean} `true` if the value is an object or function, otherwise `false`.
 *
 * @example
 * ```ts
 * console.log(isObjectLoose({})); // Output: true
 * console.log(isObjectLoose([])); // Output: true
 * console.log(isObjectLoose(() => {})); // Output: true
 * console.log(isObjectLoose(null)); // Output: false
 * console.log(isObjectLoose(42)); // Output: false
 * ```
 *
 * **Features**
 * - ✅ Recognizes **all objects** (plain objects, arrays, functions, dates, etc.).
 * - ✅ Recognizes **functions** as objects (since functions are technically objects in JavaScript).
 * - ❌ Does **not** differentiate between plain objects and special objects (like arrays, functions, DOM nodes, etc.).
 *
 * **Behavior**
 * - ✅ `isObjectLoose({})` → `true`
 * - ✅ `isObjectLoose([])` → `true`
 * - ✅ `isObjectLoose(() => {})` → `true`
 * - ❌ `isObjectLoose(null)` → `false`
 *
 * **When to use**
 * - Use `isObjectStrict` when you need a **strict check for plain objects**.
 * - Use `isObjectLoose` if you need to check if a value is an **object-like structure**, including functions.
 *
 * **Comparison**
 * | Feature                | Strict Check (`isObjectStrict`) | Loose Check (`isObjectLoose`) |
 * |------------------------|----------------------|----------------------|
 * | Recognizes plain objects | ✅ Yes | ✅ Yes |
 * | Recognizes functions    | ❌ No | ✅ Yes |
 * | Recognizes arrays       | ❌ No | ✅ Yes |
 * | Recognizes `Object.create(null)` objects | ✅ Yes | ✅ Yes |
 * | Recognizes class instances | ❌ No | ✅ Yes |
 * | Recognizes DOM elements | ❌ No | ✅ Yes |
 * | Complexity             | 🔴 High | 🟢 Low |
 */
declare const isObjectLoose: (value: unknown) => boolean;
/**
 * Checks if a given value is a class constructor.
 *
 * This function determines whether the provided value is a class by verifying
 * if it is a function and checking its prototype descriptor. Class constructors
 * always have a non-writable prototype, while regular functions do not.
 *
 * Will always return false on built in constructors like `Date` or `Array`.
 *
 * @param {unknown} value - The value to check.
 * @returns {boolean} `true` if the value is a class constructor, otherwise `false`.
 *
 * @example
 * ```ts
 * class MyClass {}
 * console.log(isClass(MyClass)); // Output: true
 *
 * function regularFunction() {}
 * console.log(isClass(regularFunction)); // Output: false
 *
 * console.log(isClass(() => {})); // Output: false
 * console.log(isClass(null)); // Output: false
 * ```
 */
declare const isClass: (value: unknown) => boolean;
/**
 * Checks if a given value is a built-in JavaScript constructor.
 *
 * This function verifies whether the provided value is a function and matches
 * one of JavaScript's built-in constructors, such as `Object`, `Array`, `Function`, etc.
 *
 * @param {unknown} value - The value to check.
 * @returns {boolean} `true` if the value is a built-in constructor, otherwise `false`.
 *
 * @example
 * ```ts
 * console.log(isBuiltInConstructor(Object)); // Output: true
 * console.log(isBuiltInConstructor(Array)); // Output: true
 * console.log(isBuiltInConstructor(class MyClass {})); // Output: false
 * console.log(isBuiltInConstructor(() => {})); // Output: false
 * console.log(isBuiltInConstructor(123)); // Output: false
 * ```
 */
declare const isBuiltInConstructor: (value: unknown) => boolean;
/**
 * Checks if a given value is an instance of a non-standard (unknown) class.
 *
 * This function determines whether the provided value is an object and has a prototype
 * that is neither `Object.prototype` (standard object) nor `null` (no prototype).
 * It helps differentiate between instances of custom classes and plain objects.
 *
 * @param {unknown} value - The value to check.
 * @returns {boolean} `true` if the value is an instance of a non-standard class, otherwise `false`.
 *
 * @example
 * ```ts
 * class MyClass {}
 * console.log(isInstanceOfUnknownClass(new MyClass())); // Output: true
 * console.log(isInstanceOfUnknownClass({})); // Output: false
 * console.log(isInstanceOfUnknownClass(Object.create(null))); // Output: false
 * console.log(isInstanceOfUnknownClass([])); // Output: true
 * ```
 */
declare const isInstanceOfUnknownClass: (value: unknown) => boolean;

export { isBoolean, isBuiltInConstructor, isClass, isInstanceOfUnknownClass, isNotBoolean, isNotNumber, isNotString, isNotUndefined, isNumber, isObjectLoose, isObjectStrict, isString, isUndefined };