Test whether a value has in its prototype chain a specified constructor as a prototype property.
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> Test whether a value has in its prototype chain a specified constructor as a prototype property.
``bash`
npm install @stdlib/assert-instance-of
`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
`
- 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
`
`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
`
*
- [@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.
*
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].
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---
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Copyright © 2016-2026. The Stdlib [Authors][stdlib-authors].
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[deno-url]: https://github.com/stdlib-js/assert-instance-of/tree/deno
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[@stdlib/assert/is-prototype-of]: https://www.npmjs.com/package/@stdlib/assert-is-prototype-of
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[@stdlib/utils/inherit]: https://www.npmjs.com/package/@stdlib/utils-inherit
[@stdlib/utils/type-of]: https://www.npmjs.com/package/@stdlib/utils-type-of