Q:

Why do we set Child constructors to themselves?

In JavaScript, in training tutorials and such you will have an Object prototype. such as:
function Animal(name) {
    this.name = name;

    speak: function() {
       console.log("Yummy!");
    }
}

and then they will make a new instance like so let dog = new Animal("FunName")
however they will feel the need to define a separate constructor for Dog?
such as Dog.prototype.constructor = Dog;
What exactly is the "point" of doing this? 

A:

JavaScript is a prototype-based language — each object has a prototype object, which acts as a template object that it inherits methods and properties from. An object's prototype object may also have a prototype object, which it inherits methods and properties from, and so on. This is often referred to as a prototype chain, and explains why different objects have properties and methods defined on other objects available to them.
The properties and methods are defined on the Objects' constructor functions, not the object instances themselves.
In classic OOP, classes are defined, then when object instances are created all the properties and methods defined on the class are copied over to the instance. In JavaScript, they are not copied over — instead, a link is made between the object instance and its constructor (a link in the prototype chain), and the properties and methods are found in the constructor by walking up the chain.
If you move ahead with oops in Javascript you will realize that certain attributes are inherited while others are not, this is because inherited ones are the ones defined on the prototype property (you could call it a sub namespace) — that is, the ones that begin with Object.prototype., and not the ones that begin with just Object. The prototype property's value is an object, which is basically a bucket for storing properties and methods that we want to be inherited by objects further down the prototype chain.
So if you want that you are able to access all the data members and functions properly, you should follow explicitly defining the constructor or else you won't be able to access few functions and data members.

