Checks if any value is an object(by using the isObject()) with keys of the PropertyKey in it(or its prototype chain) by using the in operator.

const isObjectKeysIn = <Obj = object, Payload extends object = object>(
  value: any,
  keys: PropertyKey[],
  callback: ResultCallback<
    { keys: typeof keys } & Payload
  > = resultCallback,
  payload?: Payload
): value is Obj =>
    isObject(value) && isArray(keys) ? keys.every((k) => k in value) : false,
    { ...payload, keys } as any

Generic type variables


A generic type variable Obj indicates the type of the given value parameter via the return type value is Obj, by default object.


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 isObjectKeysIn() function from which it captures its value.


value: any

The value of any type to check against the object that contains(or its prototype chain) keys from the given keys.

keys: PropertyKey[]

An Array of property keys to check if a given value contains(or its prototype chain).

callback: ResultCallback<any, { keys: typeof keys } & 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.

The payload parameter of the callback function consists of the keys property given in parameter of the core function, and it can't be overwritten by the given payload parameter of the core 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 Obj

The return type is a boolean as the result of its statement indicating the value is a generic type variable Obj by default equal to the object.


The return value is a boolean indicating whether the provided value is an object that contains(or its prototype chain) given keys.

Example usage

// Example usage.
import { isObjectKeysIn } from '@angular-package/type';

class Person {
  firstName = 'name';
  surname = 'surname';
  age = 27;
  city = 'New York';
  sex = 'Male';
  get getAge(): number {
    return this.age;
const person = new Person();
// Define property.
Object.defineProperty(person, 'notEnumerable', { enumerable: false });
person.propertyIsEnumerable('notEnumerable'); // Returns `false`.
isObjectKeysIn(person, ['firstName']); // Returns `true` as `value is object`.
isObjectKeysIn(person, ['firstName', 'surname']); // Returns `true` as `value is object`.
isObjectKeysIn(person, ['firstName', 'no property']); // Returns `false` as `value is object`.
// Getter.
isObjectKeysIn(person, ['getAge']); // Returns `true` as `value is object`.
// not enumerable.
isObjectKeysIn(person, ['notEnumerable']); // Returns `true` as `value is object`.

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