ObjectgetPrototypeOf

Object.getPrototypeOf is a built-in JavaScript function that retrieves the prototype of a given object. It is a static method on the Object constructor and is defined by the ECMAScript 5 standard. The prototype retrieved is the value of the object's internal [[Prototype]] slot, which underpins property inheritance in JavaScript objects.

Syntax and behavior: Object.getPrototypeOf(object) returns the object's immediate prototype. If the argument is a primitive value, it is boxed to its wrapper object and the wrapper's prototype is returned. If the argument is null or undefined, the call throws a TypeError because null and undefined do not have a prototype.

Examples: Object.getPrototypeOf({}) yields Object.prototype; Object.getPrototypeOf([]) yields Array.prototype; Object.getPrototypeOf(function(){}) yields Function.prototype. For an object created with no prototype, such as Object.create(null), Object.getPrototypeOf(obj) returns null.

Usage notes: Object.getPrototypeOf is the standard and recommended way to inspect an object's prototype. It is preferred over the deprecated __proto__ property and can be used to test inheritance with strict equality checks (e.g., objProto === SomePrototype). Related functions include Object.setPrototypeOf and Object.create.

Compatibility: Introduced in ES5 and supported by all modern browsers and Node.js versions.