Module is/instanceOf

isInstanceOf

• isInstanceOf<T>(target: unknown, declaration: Constructor<T>, loose?: boolean): target is T

• Performs a loose instance check by comparing class names up the prototype chain if instanceof initially fails. To disable this loose check, pass false as the 3rd argument.

  import { isInstanceOf } from 'tily/is/instanceOf';
  
  if (isInstanceOf(error, Error)) {
      console.log(error.stack);
  }
  

  Generics can be used to type the object being checked. This will default to the declaration passed to the 2nd argument.

  isInstanceOf<ParseError>(error, Error);
  

  Loose checks can be useful if multiple copies of the same class declaration exists in the module tree. For example, multiple versions of the same package are imported.

  example

   isInstanceOf(undefined, Foo);           //=> false
   isInstanceOf(null, Foo);                //=> false
  
   class Foo {}
   class Bar {}
  
   isInstanceOf(new Foo(), Foo);           //=> true
   isInstanceOf(new Bar(), Foo);           //=> false
  
   class Baz {}
   Object.defineProperty(Baz, 'name', { value: 'Foo' });
  
   isInstanceOf(new Baz(), Foo);           //=> true
   isInstanceOf(new Baz(), Foo, false);    //=> false
  

  Type parameters

  • T = unknown

  Parameters

  • target: unknown

    The object to check

  • declaration: Constructor<T>

    The constructor

  • loose: boolean = true

    Whether use loose checks. Default is true.

  Returns target is T