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is ​

is is a namespace object that groups the core type and comparison helpers under a single import.

Signature ​

ts
const is: {
  array(value: unknown): value is unknown[];
  boolean(value: unknown): value is boolean;
  date(value: unknown): value is Date;
  defined<T>(value: T | undefined): value is T;
  empty(value: unknown): boolean;
  equal<T>(a: T, b: T): boolean;
  fn(value: unknown): value is (...args: any[]) => unknown;
  match<T extends object>(object: unknown, source: Partial<T>): object is T;
  nil(value: unknown): value is null | undefined;
  number(value: unknown): value is number;
  object(value: unknown): value is Record<string, unknown>;
  primitive(value: unknown): value is string | number | boolean;
  promise<T = unknown>(value: unknown): value is Promise<T>;
  regex(value: unknown): value is RegExp;
  string(value: unknown): value is string;
  typeOf(value: unknown): string;
};

Examples ​

Common checks ​

ts
import { is } from '@vielzeug/toolkit';

is.string('hello'); // true
is.number(42); // true
is.array([1, 2, 3]); // true
is.nil(undefined); // true
is.defined('x'); // true
is.empty({}); // true

Equality and pattern matching ​

ts
import { is } from '@vielzeug/toolkit';

is.equal({ a: 1 }, { a: 1 }); // true
is.match({ a: 1, b: 2 }, { a: 1 }); // true

Runtime type tags ​

ts
import { is } from '@vielzeug/toolkit';

is.typeOf('hello'); // 'string'
is.typeOf([1, 2]); // 'array'
is.typeOf(new Date()); // 'date'