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    @stdlib/assert-is-prototype-of
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    0.0.7 • Public • Published

    isPrototypeOf

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    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


    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.

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    License

    See LICENSE.

    Copyright

    Copyright © 2016-2022. The Stdlib Authors.

    Install

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

    Homepage

    stdlib.io

    DownloadsWeekly Downloads

    49

    Version

    0.0.7

    License

    Apache-2.0

    Unpacked Size

    39.7 kB

    Total Files

    9

    Last publish

    Collaborators

    • stdlib-bot
    • kgryte
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