guardType()
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guardType()
Guards the value to be a type of given type
.
const guardType = <T extends Type, Payload extends object = object>(
value: T,
type: Types<T>,
callback?: ResultCallback<T, Payload>,
payload?: Payload
): value is T => isType(value, type, callback, payload);
T
extends
Type
A generic type variable T
constrained by generic type Type
indicates captured type of the supplied value
via the return type and the value
parameter of the provided callback
function ResultCallback
type.
Payload
extends
object
=
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 guardType()
function from which it captures its value.
value: T
The value of a generic type variable T
constrained by generic type Type
, by default of the type captured from itself, to guard.
type: Types<T>
The value of string
or Constructor<T>
type of the Types
indicates against which type a given value
is checked.
callback?: ResultCallback<T, Payload>
The optional 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.
value is
T
The return type is a boolean
as the result of its statement indicating the value
is a generic type variable T
by default of the type captured from the supplied value
.
The return value is a boolean
indicating whether the value
is a type from a given type
of the Types
.
// Example usage.
import { guardType } from '@angular-package/type';
// Person interface.
interface PersonData { firstName: string; }
// Class.
class Person {}
// Object.
const someone: Person = new Person();
const object: PersonData = { firstName: 'firstName' };
guardType(object, 'object'); // true; return type `value is PersonData`
let letObject: PersonData = { firstName: 'firstName' };
guardType(letObject, 'object'); // true; return type `value is PersonData`
function myPerson(person: Person): Person { return person; }
guardType(myPerson, 'function'); // true; return type `value is (person: Person) => Person`
// string.
const firstName = 'firstName';
guardType(firstName, 'string'); // true; return type `value is "firstName"`
let letFirstName = 'firstName';
guardType(letFirstName, 'string'); // true; return type `value is string`
// number.
const age = 5;
guardType(age, 'number'); // true; return type `value is 5`
let letAge = 5;
guardType(letAge, 'number'); // true; return type `value is number`
// null.
const myNull = null;
guardType(myNull, 'null'); // true; return type `value is null`
// bigint
const oldAge = 1n;
guardType(oldAge, 'bigint'); // true; return type `value is 1n`
let letOldAge = 1n;
guardType(letOldAge, 'bigint'); // true; return type `value is bigint`
// Boolean.
const question = true;
guardType(question, 'boolean'); // true; return type `value is true`
let letQuestion = true;
guardType(letQuestion, 'boolean'); // true; return type `value is true`
// Undefined.
const und = undefined;
guardType(und, 'undefined'); // true; return type `value is undefined`
let letUndefined ;
guardType(letUndefined, 'undefined'); // true; return type `value is undefined`
// Symbol.
guardType(Symbol(firstName), 'symbol'); // true; return type `value is symbol`
// Instance.
guardType(someone, Person); // true; return type `value is Person`