@stdlib/assert-is-prototype-of

About stdlib...

We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.

The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.

When you use stdlib, you can be absolutely certain that you are using the most thorough, rigorous, well-written, studied, documented, tested, measured, and high-quality code out there.

To join us in bringing numerical computing to the web, get started by checking us out on GitHub, and please consider financially supporting stdlib. We greatly appreciate your continued support!

isPrototypeOf

Test if an object's prototype chain contains a provided prototype.

Installation

npm install @stdlib/assert-is-prototype-of

Usage

var isPrototypeOf = require( '@stdlib/assert-is-prototype-of' );

isPrototypeOf( obj, prototype )

Tests if an object's prototype chain contains a provided prototype.

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

function Foo() {
    return this;
}

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

var bar = new Bar();

var bool = isPrototypeOf( bar, Foo.prototype );
// returns true

Notes

• The function returns false if provided a primitive value.

  var Number = require( '@stdlib/number-ctor' );
  
  var bool = isPrototypeOf( 5, Number.prototype );
  // returns false
  
  bool = isPrototypeOf( 'beep', String.prototype );
  // returns false
  
  bool = isPrototypeOf( true, Boolean.prototype );
  // returns false

• The function throws a TypeError if provided a prototype value which is neither an object (except null) or a function.

  var bool = isPrototypeOf( Object.create( null ), null );
  // throws <TypeError>

• isPrototypeOf() is generally more robust than the instanceof operator. Consider the following example which does not use constructors:

  // Functionally similar to `Object.create()`...
  function createObject( proto ) {
      function Ctor() {
          // Empty constructor...
      }
      Ctor.prototype = proto;
      return new Ctor();
  }
  var superProto = {
      'beep': 'beep'
  };
  
  var subProto = createObject( superProto );
  subProto.boop = 'boop';
  
  var v = createObject( subProto );
  
  var bool;
  try {
      bool = ( v instanceof superProto );
  } catch ( error ) {
      // Encountered a type error...
      console.error( error.message );
  }
  
  bool = isPrototypeOf( v, superProto );
  // returns true

Examples

var inherit = require( '@stdlib/utils-inherit' );
var isPrototypeOf = require( '@stdlib/assert-is-prototype-of' );

function A() {
    return this;
}

function B() {
    return this;
}
inherit( B, A );

function C() {
    return this;
}
inherit( C, B );

function D() {
    return this;
}
inherit( D, C );

var a = new A();
var b = new B();
var c = new C();
var d = new D();

var bool = isPrototypeOf( d, C.prototype );
// returns true

bool = isPrototypeOf( d, B.prototype );
// returns true

bool = isPrototypeOf( d, A.prototype );
// returns true

bool = isPrototypeOf( c, B.prototype );
// returns true

bool = isPrototypeOf( c, A.prototype );
// returns true

bool = isPrototypeOf( c, D.prototype );
// returns false

bool = isPrototypeOf( b, A.prototype );
// returns true

bool = isPrototypeOf( b, C.prototype );
// returns false

bool = isPrototypeOf( b, D.prototype );
// returns false

bool = isPrototypeOf( a, B.prototype );
// returns false

bool = isPrototypeOf( a, C.prototype );
// returns false

bool = isPrototypeOf( a, D.prototype );
// returns false

---

See Also

• @stdlib/utils-get-prototype-of: return the prototype of a provided object.

---

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 © 2016-2024. The Stdlib Authors.