在此页

• 句法
• 描述
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

isPrototypeOf() method checks if an object exists in another object's prototype chain.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

isPrototypeOf() differs from the instanceof operator. In the expression " object instanceof AFunction ", the object prototype chain is checked against AFunction.prototype , not against AFunction 本身。

句法

prototypeObj.isPrototypeOf(object)
					

参数

object

The object whose prototype chain will be searched.

返回值

A 布尔 indicating whether the calling object lies in the prototype chain of the specified object.

Errors thrown

TypeError

TypeError is thrown if prototypeObj is undefined or null.

描述

isPrototypeOf() method allows you to check whether or not an object exists within another object's prototype chain.

范例

Using isPrototypeOf

This example demonstrates that Baz.prototype , Bar.prototype , Foo.prototype and Object.prototype exist in the prototype chain for object baz :

function Foo() {}
function Bar() {}
function Baz() {}
Bar.prototype = Object.create(Foo.prototype);
Baz.prototype = Object.create(Bar.prototype);
var baz = new Baz();
console.log(Baz.prototype.isPrototypeOf(baz)); // true
console.log(Bar.prototype.isPrototypeOf(baz)); // true
console.log(Foo.prototype.isPrototypeOf(baz)); // true
console.log(Object.prototype.isPrototypeOf(baz)); // true
					

isPrototypeOf() method, along with the instanceof operator particularly comes in handy if you have code that can only function when dealing with objects descended from a specific prototype chain, e.g., to guarantee that certain methods or properties will be present on that object.

For example, check if baz object descends from Foo.prototype :

if (Foo.prototype.isPrototypeOf(baz)) {
  // do something safe
}
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Object.prototype.isPrototypeOf' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
isPrototypeOf	Chrome 1	Edge 12	Firefox 1	IE 9	Opera 4	Safari 3	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs Yes

图例

完整支持

完整支持

另请参阅

• instanceof
• Object.getPrototypeOf()
• Object.setPrototypeOf()
• Object.prototype.__proto__

元数据

• 最后修改： May 8, 2020

相关话题

1. 标准内置对象
2. Object
3. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
4. 方法
   1. Object.assign()
   2. Object.create()
   3. Object.defineProperties()
   4. Object.defineProperty()
   5. Object.entries()
   6. Object.freeze()
   7. Object.fromEntries()
   8. Object.getOwnPropertyDescriptor()
   9. Object.getOwnPropertyDescriptors()
   10. Object.getOwnPropertyNames()
   11. Object.getOwnPropertySymbols()
   12. Object.getPrototypeOf()
   13. Object.is()
   14. Object.isExtensible()
   15. Object.isFrozen()
   16. Object.isSealed()
   17. Object.keys()
   18. Object.preventExtensions()
   19. Object.prototype.__defineGetter__()
   20. Object.prototype.__defineSetter__()
   21. Object.prototype.__lookupGetter__()
   22. Object.prototype.__lookupSetter__()
   23. Object.prototype.hasOwnProperty()
   24. Object.prototype.isPrototypeOf()
   25. Object.prototype.propertyIsEnumerable()
   26. Object.prototype.toLocaleString()
   27. Object.prototype.toSource()
   28. Object.prototype.toString()
   29. Object.prototype.valueOf()
   30. Object.seal()
   31. Object.setPrototypeOf()
   32. Object.values()
5. 继承：
6. Function
7. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
8. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()