Module is/instance

isInstance

• isInstance<T>(declaration: Constructor<T>, target: unknown, loose?: boolean): target is T
• isInstance<T>(declaration: Constructor<T>): (target: unknown, 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 { isInstance } from 'tily/is/instance';
  
  if (isInstance(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.

  isInstance<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

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

  Type parameters

  • T = unknown

  Parameters

  • declaration: Constructor<T>

    The constructor

  • target: unknown

    The object to check

  • Optional loose: boolean

    Whether use loose checks. Default is true.

  Returns 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 { isInstance } from 'tily/is/instance';
  
  if (isInstance(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.

  isInstance<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

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

  Type parameters

  • T = unknown

  Parameters

  • declaration: Constructor<T>

    The constructor

  Returns (target: unknown, loose?: boolean) => target is T

  • • (target: unknown, loose?: boolean): target is T

    • Parameters

      • target: unknown

      • Optional loose: boolean

      Returns target is T