Checks if any value is one of the string, number, or symbol type.

const isKey = <Payload extends object>(
  value: any,
  callback: ResultCallback<any, Payload> = resultCallback,
  payload?: Payload
): value is PropertyKey =>
    isStringType(value) || isNumberType(value) || isSymbol(value),

Generic type variables


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 isKey() 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 PropertyKey

The return type is a boolean as the result of its statement indicating the value is PropertyKey.


The return value is a boolean indicating whether the provided value is a PropertyKey.

Example usage

Key of string

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

const STRING = 'surname';
const STRING_INSTANCE = new String(STRING);
isKey(STRING); // true
isKey(STRING_INSTANCE); // true

Key of number

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

const NUMBER = 27;
const NUMBER_INSTANCE = new Number(NUMBER);
isKey(NUMBER); // true
isKey(NUMBER_INSTANCE); // true

Key of symbol

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

const STRING = 'surname';
const NUMBER = 27;

const SYMBOL_NUMBER: unique symbol = Symbol(NUMBER);
const SYMBOL_STRING: unique symbol = Symbol(STRING);

isKey(SYMBOL_NUMBER); // true
isKey(SYMBOL_STRING); // true

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