Object.prototype.__proto__ - JavaScript | MDN

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Object.getPrototypeOf()

Note: The use of __proto__ is controversial and discouraged. Its existence and exact behavior have only been standardized as a legacy feature to ensure web compatibility, while it presents several security issues and foo

Reflect.getPrototypeOf()

Note: The use of __proto__ is controversial and discouraged. Its existence and exact behavior have only been standardized as a legacy feature to ensure web compatibility, while it presents several security issues and foo

Object.setPrototypeOf()

Note: The use of __proto__ is controversial and discouraged. Its existence and exact behavior have only been standardized as a legacy feature to ensure web compatibility, while it presents several security issues and foo

Reflect.setPrototypeOf()

Note: The use of __proto__ is controversial and discouraged. Its existence and exact behavior have only been standardized as a legacy feature to ensure web compatibility, while it presents several security issues and foo

object initializer / literal syntax

Note: The use of __proto__ is controversial and discouraged. Its existence and exact behavior have only been standardized as a legacy feature to ensure web compatibility, while it presents several security issues and foo

Function.prototype

The __proto__ getter function exposes the value of the internal [[Prototype]] of an object. For objects created using an object literal (unless you use the prototype setter syntax), this value is Object.prototype. For ob

Inheritance and the prototype chain

The __proto__ getter function exposes the value of the internal [[Prototype]] of an object. For objects created using an object literal (unless you use the prototype setter syntax), this value is Object.prototype. For ob

null-prototype objects

The __proto__ getter function exposes the value of the internal [[Prototype]] of an object. For objects created using an object literal (unless you use the prototype setter syntax), this value is Object.prototype. For ob

Object.defineProperty()

The __proto__ getter function exposes the value of the internal [[Prototype]] of an object. For objects created using an object literal (unless you use the prototype setter syntax), this value is Object.prototype. For ob

Object.prototype.isPrototypeOf()

Prototype pollution attack

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This page was last modified on Aug 21, 2026 by MDN contributors.

defineProperties()

getOwnPropertyDescriptor()

getOwnPropertyDescriptors()

getOwnPropertyNames()