instanceOf

Installation

npm install @stdlib/assert-instance-of

Alternatively,

• To load the package in a website via a script tag without installation and bundlers, use the ES Module available on the esm branch.
• If you are using Deno, visit the deno branch.
• For use in Observable, or in browser/node environments, use the Universal Module Definition (UMD) build available on the umd branch.

The branches.md file summarizes the available branches and displays a diagram illustrating their relationships.

Usage

var instanceOf = require( '@stdlib/assert-instance-of' );

instanceOf( value, constructor )

Tests whether a value has in its prototype chain a specified constructor as a prototype property.

var inherit = require( '@stdlib/utils-inherit' );

function Foo() {
    return this;
}

function Bar() {
    return this;
}
inherit( Bar, Foo );

var bar = new Bar();

var bool = instanceOf( bar, Foo );
// returns true

Notes

• The function throws a TypeError if provided a constructor argument which is not callable.

  var bool = instanceOf( {}, null );
  // throws <TypeError>

• While the prototype of an object created using object literal notion is undefined, the function returns true when provided an object literal and the Object constructor. This maintains consistent behavior with the instanceof operator.

  var bool = ( {} instanceof Object );
  // returns true
  
  bool = instanceOf( {}, Object );
  // returns true

Examples

var Number = require( '@stdlib/number-ctor' );
var instanceOf = require( '@stdlib/assert-instance-of' );

var bool = instanceOf( [], Array );
// returns true

bool = instanceOf( [], Object );
// returns true

bool = instanceOf( {}, Object );
// returns true

bool = instanceOf( new Date(), Date );
// returns true

bool = instanceOf( /.*/, RegExp );
// returns true

bool = instanceOf( instanceOf, Function );
// returns true

bool = instanceOf( null, Object );
// returns false

bool = instanceOf( 5, Number );
// returns false

bool = instanceOf( '5', String );
// returns false

bool = instanceOf( void 0, Object );
// returns false

bool = instanceOf( {}, Array );
// returns false

bool = instanceOf( {}, Function );
// returns false

See Also

• @stdlib/assert/is-prototype-of: test if an object's prototype chain contains a provided prototype.
• @stdlib/utils/constructor-name: determine the name of a value's constructor.
• @stdlib/utils/inherit: implement prototypical inheritance by replacing the prototype of one constructor with the prototype of another constructor.
• @stdlib/utils/type-of: determine a value's type.

Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

Community

License

See LICENSE.

Copyright

Copyright © 2016-2022. The Stdlib Authors.