Test if an object's prototype chain contains a provided prototype.
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> Test if an object's prototype chain contains a provided prototype.
``bash`
npm install @stdlib/assert-is-prototype-of
`javascript`
var isPrototypeOf = require( '@stdlib/assert-is-prototype-of' );
#### isPrototypeOf( obj, prototype )
Tests if an object's prototype chain contains a provided prototype.
`javascript
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
`
- The function returns false if provided a primitive value.
`javascript
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.
`javascript`
var bool = isPrototypeOf( Object.create( null ), null );
// throws
- isPrototypeOf() is generally more robust than the instanceof operator. Consider the following example which does not use constructors:
`javascriptObject.create()
// Functionally similar to ...
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
`
`javascript
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
`
*
- [@stdlib/utils-get-prototype-of][@stdlib/utils/get-prototype-of]: return the prototype of a provided object.
*
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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[@stdlib/utils/get-prototype-of]: https://www.npmjs.com/package/@stdlib/utils-get-prototype-of