Why, in the result of this object type intersection, is the type of the `constructor` property intersected with `Function`?

Question

If I perform this type intersection:

{ constructor: 'FooConstructor', value1: boolean } & { value2: number };

The resulting type is this:

{ constructor: 'FooConstructor' & Function, value1: boolean, value2: number };

(Playground example)

Why is the type of the resulting constructor property intersected with Function?

Answer 1

This is because:

• The type { constructor: 'FooConstructor', value1: boolean } & { value2: number } is a subtype of object, because every object type is.
• The type object['constructor'] is Function.

And that's because objects in Javascript do have a property named constructor which refers to the function used to construct them:

> let obj = {};
> obj.constructor
ƒ Object() { [native code] }

I suggest using a property name like constructor_ or constructorName instead, since constructor is meant to refer to an actual constructor.