isArray

The isArray utility is a type guard that checks if a given value is an array. It provides reliable detection across different execution environments.

Implementation

View Source Code

/**
 * Determines if the passed value is an array.
 *
 * @example
 * ```ts
 * isArray([1, 2, 3]) // true
 * isArray(1, 2, 3) // false
 * ```
 *
 * @param arg - The argument to be checked.
 *
 * @returns `true` if the value is an array, else `false`.
 */
export function isArray(arg: unknown): arg is Array<unknown> {
  return Array.isArray(arg);
}

export const IS_ARRAY_ERROR_MSG = 'Expected an array';

Features

• Isomorphic: Works in both Browser and Node.js.
• Type Guard: Automatically narrows the type of the checked value to any[] or unknown[] within conditional blocks.
• Reliable: Correctly identifies arrays even when they originate from different iframes or windows.

API

function isArray(value: unknown): value is any[];

Parameters

• value: The value to check.

Returns

• true if the value is an array; otherwise, false.

Examples

Basic Usage

import { isArray } from '@vielzeug/toolkit';

isArray([1, 2, 3]); // true
isArray('hello'); // false
isArray({}); // false

Type Narrowing

import { isArray } from '@vielzeug/toolkit';

function process(data: unknown) {
  if (isArray(data)) {
    // data is now typed as any[]
    return data.length;
  }
  return 0;
}

Implementation Notes

• Internally uses the native Array.isArray() method.
• Throws nothing; safely handles null, undefined, and all other primitive or object types.

See Also

• isObject: Check if a value is a plain object.
• isEmpty: Check if an array (or object/string) is empty.
• isDefined: Check if a value is not null or undefined.