Checks if the value is not the type obtained from its object class equal to 'string', not a string type and not an instance of String.

const isNotString = <Type, Payload extends object = object>(
  value: Type,
  callback: ResultCallback<Type, Payload> = resultCallback,
  payload?: Payload
): value is Never<AnyString, Type> =>
    typeOf(value) !== 'string' &&
      typeof value !== 'string' &&
      value instanceof String === false,

Generic type variables


A generic type variable Type indicates the captured type of the given value via the return type value is Never<AnyString, Type> and the value parameter of the provided callback function ResultCallback type.


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 isNotString() function from which it captures its value.


value: Type

The value of generic type variable Type, by default of the type captured from itself to check.

callback: ResultCallback<Type, 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 Never<AnyString, Type>

The return type is a boolean as the result of its statement indicating the value is a generic type Never that takes a generic type variable Type from the supplied value and not equal to AnyString, which makes it never AnyString but of type captured from the supplied value.


The return value is a boolean indicating whether the provided value is not a string and not an instance of String.

Example usage

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

const anyString: any = 'any string';
const firstName = 'firstName';
const age = 27;
const objectString = new String('hold me');

isNotString(anyString); // return type is `value is any`
isNotString(firstName); // return type is `value is never`
isNotString(age); // return type is `value is number`
isNotString(objectString); // return type is `value is never`

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