Test if an object's prototype chain contains a provided prototype.
APACHE-2.0 License
Test if an object's prototype chain contains a provided prototype.
npm install @stdlib/assert-is-prototype-of
Alternatively,
script
tag without installation and bundlers, use the ES Module available on the esm
branch (see README).deno
branch (see README for usage intructions).umd
branch (see README).The branches.md 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.
var isPrototypeOf = require( '@stdlib/assert-is-prototype-of' );
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
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
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
: return the prototype of a provided object.
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.
See LICENSE.
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