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  5. Object
  6. Object.prototype.isPrototypeOf()
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Object.prototype.isPrototypeOf()

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since 2015 ..

isPrototypeOf() , .

: isPrototypeOf() instanceof. "object instanceof AFunction" , object AFunction.prototype, AFunction.

In this article

prototypeObj.isPrototypeOf(object)

prototypeObj

, object.

object

, .

isPrototypeOf() , .

, :

js
function Fee() {
  // ...
}

function Fi() {
  // ...
}
Fi.prototype = new Fee();

function Fo() {
  // ...
}
Fo.prototype = new Fi();

function Fum() {
  // ...
}
Fum.prototype = new Fo();

Fum , Fi Fum, :

js
var fum = new Fum();
// ...

if (Fi.prototype.isPrototypeOf(fum)) {
  //   - 
}

, instanceof, , , , , , , .

Specification
ECMAScript 2027 LanguageSpecification
# sec-object.prototype.isprototypeof

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  2. Object
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    1. Object.prototype.__defineGetter__()
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    4. Object.prototype.__lookupSetter__()
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    1. Object.prototype.__proto__
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    2. Object.prototype.__defineSetter__()
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