empty-php/src/empty.ts

Exact replica of the PHP empty function in for JavaScript and TypeScript

import type {Empty, EmptyArray, EmptyBoolean, EmptyNumber, EmptyObject, EmptyString, Undefined} from "./types";

/**
 * Determines if a boolean is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: boolean | Undefined): value is EmptyBoolean;

/**
 * Determines if a string is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: string | Undefined): value is EmptyString;

/**
 * Determines if a number is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: number | Undefined): value is EmptyNumber;

/**
 * Determines if an array is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: unknown[] | Undefined): value is EmptyArray;

/**
 * Determines if a complex object is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty<T extends object>(value?: T | Undefined): value is Undefined;

/**
 * Determines if an object is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: object | Undefined): value is EmptyObject;

/**
 * Determines if the input value is empty
 * @param value The value to determine if empty
 * @returns true if the value is empty, false otherwise
 * @see https://www.php.net/manual/en/function.empty.php
 */
export function empty(value?: unknown): value is Empty {
    // If value is null on undefined:
    if (value == null) return true;

    // By types:
    if ('boolean' == typeof value) return !value;
    if ('number' == typeof value) return value === 0;
    if ('string' == typeof value) return value === '0' || value.length === 0;

    // Empty arrays:
    if (Array.isArray(value)) return value.length === 0;

    // Empty objects:
    if (value.toString == Object.prototype.toString) {
        switch (value.toString()) {
            case '[object File]':
            case '[object Map]':
            case '[object Set]': {
                // @ts-expect-error Artifact from TS migration
                return value.size === 0
            }
            case '[object Object]': {
                for (let key in value) {
                    if (Object.prototype.hasOwnProperty.call(value, key)) return false
                }

                return true
            }
        }
    }

    // Everything else...
    return false
}