Checks if any value is of the type obtained from its object class equal to 'array' or an object type and passes the test Array.isArray() method.

const isArray = <Type = any, Payload extends object = object>(
  value: any,
  callback: ResultCallback<any, Payload> = resultCallback,
  payload?: Payload
): value is Array<Type> =>
    (typeOf(value) === 'array' || typeof value === 'object') &&

Generic type variables


The Type generic type variable indicates the array element type of the given value via the return type, by default is any.


The Payload generic type variable constrained by object indicates the type of optional parameter payload of the supplied callback function and payload optional parameter of the isArray() function from which it captures its value.


value: any

The value of any type to check.

callback: ResultCallback<any, Payload>

A callback function of ResultCallback type with parameters, the value that has been checked, the result of this check, and payload of generic type variable Payload with optional properties from the provided payload, to handle them before the result return. By default, it uses resultCallback() function.

payload?: Payload

An optional object of the generic type variable Payload is assigned to the payload of the given callback function.

Return type

value is Array<Type>

The return type is a boolean because of used the is operator indicating the value is an array that takes generic type variable Type by default of value any as the type of its elements.


The return value is a boolean indicating whether the provided value is an Array.

Example usage

Basic example

// Basic example.
import { isArray } from '@angular-package/type'; 

const ARRAY_NUMBER = [1, 2, 3];
const ARRAY_STRING = ['a', 'b', 'c'];

isArray(ARRAY_NUMBER); // Returns `true` as `value is any[]`
isArray<string>(ARRAY_STRING); // Returns `true` as `value is string[]`

Fake array

// Fake array example.
import { isArray } from '@angular-package/type'; 

const fakeArray = new String('');

Object.assign(fakeArray, {
  get [Symbol.toStringTag](): string {
    return 'array';

isArray(fakeArray), // false
typeOf(fakeArray), // "array"
typeof fakeArray, // "object"
Array.isArray(fakeArray) // false

Parameters callback and payload

// Example usage with callback and payload.
import { isArray } from '@angular-package/type';

isArray([1, 2, 3], (result, value, payload) => {
  if (result === true) {
    // Returns `(3) [1, 2, 3]`

    if (payload) {
      // Returns `{ "1": "First", "2": "Second", "3": "Third" }`
  return result;
  // Returns `true` as `value is any[]`
}, { transform: { 1: 'First', 2: 'Second', 3: 'Third'} }); 

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