If some other _proto_ property is found before Object.prototype is consulted, that property will hide the one found on Object.prototype. A property access for _proto_ that eventually consults Object.prototype will find this property, but an access that does not consult Object.prototype will not. The _proto_ property is a simple accessor property on Object.prototype consisting of a getter and setter function. Unlike Object.getPrototypeOf() and tPrototypeOf(), which are always available on Object as static properties and always reflect the ] internal property, the _proto_ property doesn't always exist as a property on all objects, and as a result doesn't reflect ] reliably. Providing any other value will do nothing. The value provided must be an object or null.

The _proto_ setter allows the ] of an object to be mutated. You can read more about the prototype chain in Inheritance and the prototype chain. For functions, this value is Function.prototype. For objects created using array literals, this value is Array.prototype. For objects created using an object literal, this value is Object.prototype. The _proto_ getter function exposes the value of the internal ] of an object. Object.prototype._lookupSetter_() Deprecated.Object.prototype._lookupGetter_() Deprecated.Object.prototype._defineSetter_() Deprecated.Object.prototype._defineGetter_() Deprecated.

What is prototype in javascript