Created at 281 days ago

The prototype chain for `Function()` constructor and `Function` objects

In javascript, each object has a prototype object, which can be accessed by a __proto__ accessor. And each Function object has a prototype property since it can be used as a constructor, the prototype property holds the common methods and properties of all instances.

Function() constructor is used to create Function objects. Since Function() constructor itself is a Function object, its __proto__ will be equal to Function.prototype, this is to say Function.__proto__ === Function.prototype.

const Foo = new Function()
const foo = new Foo()

foo.prototype // undefined
foo.__proto__ === Foo.prototype // true

Foo.prototype // {}
typeof Foo.prototype // 'object'
Foo.__proto__ === Function.prototype // true

typeof Function.prototype // 'function'
Function.__proto__ === Function.prototype // true

Function.prototype.prototype // undefined
Function.prototype.__proto__ === Object.prototype // true

typeof Object.prototype // 'object'
Object.prototype.prototype // undefined
Object.prototype.__proto__ === null // true

// FYI, `__proto__` is non-standard but de-facto implemented by many JavaScript engines