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https://github.com/stdlib-js/assert-instance-of

Test whether a value has in its prototype chain a specified constructor as a prototype property.
https://github.com/stdlib-js/assert-instance-of

assert assertion class inherit inheritance inherits instanceof javascript node node-js nodejs object-oriented oop proto prototype stdlib util utilities utility utils

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

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README 

        



  

    About stdlib...

  

  
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# instanceOf



[![NPM version][npm-image]][npm-url] [![Build Status][test-image]][test-url] [![Coverage Status][coverage-image]][coverage-url] 



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



## Installation



```bash

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][es-module] available on the [`esm`][esm-url] branch (see [README][esm-readme]).

-   If you are using Deno, visit the [`deno`][deno-url] branch (see [README][deno-readme] for usage intructions).

-   For use in Observable, or in browser/node environments, use the [Universal Module Definition (UMD)][umd] build available on the [`umd`][umd-url] branch (see [README][umd-readme]).



The [branches.md][branches-url] file summarizes the available branches and displays a diagram illustrating their relationships.



To view installation and usage instructions specific to each branch build, be sure to explicitly navigate to the respective README files on each branch, as linked to above.



## Usage



```javascript

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.



```javascript

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.



    ```javascript

    var bool = instanceOf( {}, null );

    // throws 

    ```



-   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.



    



    



    ```javascript

    var Object = require( '@stdlib/object-ctor' );



    var bool = ( {} instanceof Object );

    // returns true



    bool = instanceOf( {}, Object );

    // returns true

    ```



## Examples



```javascript

var Number = require( '@stdlib/number-ctor' );

var Object = require( '@stdlib/object-ctor' );

var Function = require( '@stdlib/function-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`][@stdlib/assert/is-prototype-of]: test if an object's prototype chain contains a provided prototype.

-   [`@stdlib/utils-constructor-name`][@stdlib/utils/constructor-name]: determine the name of a value's constructor.

-   [`@stdlib/utils-inherit`][@stdlib/utils/inherit]: implement prototypical inheritance by replacing the prototype of one constructor with the prototype of another constructor.

-   [`@stdlib/utils-type-of`][@stdlib/utils/type-of]: determine a value's type.



* * *



## Notice



This package is part of [stdlib][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][stdlib], see the main project [repository][stdlib].



#### Community



[![Chat][chat-image]][chat-url]



---



## License



See [LICENSE][stdlib-license].



## Copyright



Copyright © 2016-2024. The Stdlib [Authors][stdlib-authors].



[npm-image]: http://img.shields.io/npm/v/@stdlib/assert-instance-of.svg

[npm-url]: https://npmjs.org/package/@stdlib/assert-instance-of



[test-image]: https://github.com/stdlib-js/assert-instance-of/actions/workflows/test.yml/badge.svg?branch=main

[test-url]: https://github.com/stdlib-js/assert-instance-of/actions/workflows/test.yml?query=branch:main



[coverage-image]: https://img.shields.io/codecov/c/github/stdlib-js/assert-instance-of/main.svg

[coverage-url]: https://codecov.io/github/stdlib-js/assert-instance-of?branch=main



[chat-image]: https://img.shields.io/gitter/room/stdlib-js/stdlib.svg

[chat-url]: https://app.gitter.im/#/room/#stdlib-js_stdlib:gitter.im



[stdlib]: https://github.com/stdlib-js/stdlib



[stdlib-authors]: https://github.com/stdlib-js/stdlib/graphs/contributors



[umd]: https://github.com/umdjs/umd

[es-module]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Modules



[deno-url]: https://github.com/stdlib-js/assert-instance-of/tree/deno

[deno-readme]: https://github.com/stdlib-js/assert-instance-of/blob/deno/README.md

[umd-url]: https://github.com/stdlib-js/assert-instance-of/tree/umd

[umd-readme]: https://github.com/stdlib-js/assert-instance-of/blob/umd/README.md

[esm-url]: https://github.com/stdlib-js/assert-instance-of/tree/esm

[esm-readme]: https://github.com/stdlib-js/assert-instance-of/blob/esm/README.md

[branches-url]: https://github.com/stdlib-js/assert-instance-of/blob/main/branches.md



[stdlib-license]: https://raw.githubusercontent.com/stdlib-js/assert-instance-of/main/LICENSE



[@stdlib/assert/is-prototype-of]: https://github.com/stdlib-js/assert-is-prototype-of



[@stdlib/utils/constructor-name]: https://github.com/stdlib-js/utils-constructor-name



[@stdlib/utils/inherit]: https://github.com/stdlib-js/utils-inherit



[@stdlib/utils/type-of]: https://github.com/stdlib-js/utils-type-of