Why prototype consider in object but not in function instead

From this MDN, it made the appearance that prototype is a property of Object, however it seems more like prototype is a property of function instead?

Given the below code it's hitting TypeReference

let Animal = {
  name: 'randomAnimal'
}

Animal.prototype.speak = function () {
  console.log(this.name + ' makes a noise.');
}

In order to make it work, instead of object, we change it to function instead as below

function Animal (name) {
  this.name = name;  
}

Animal.prototype.speak = function () {
  console.log(this.name + ' makes a noise.');
}

My question is more on try to understand the morale or reason behind why saying prototype is consider property of object, although one can argue that all functions are objects

Solution

Prototype is an object property and functions are first class objects.

To make an object parameterizable during instantiation, we can create an object by means of a constructor function which is as you wrote:

function Animal (name) {
    this.name = name;  
}
Animal.prototype.speak = function() {
    console.log(this.name + " says hi!");
}
var lion = new Animal("lion");
lion.speak(); // "lion says hi!"

Here a name is given at the object construction.

But you can create objects also by using object initializers, like

let lion = { 
    name: "lion",
    speak: function() {
        console.log(this.name + " says hi!");
    }
}
lion.speak(); // "lion says hi!"

Naturally it is easier with a constructor, especially if you have several properties to initialize and/or several similar objects to construct.

Third way to create objects is to use Object.create(). It allows you to specify the prototype object on object creation, like:

var cat = Object.create(lion);
cat.name = "house cat";
cat.speak(); // "house cat says hi!"
console.log(lion.isPrototypeOf(cat)); // true

For info about objects in JavaScript, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects

Edit: But by default all functions have a "prototype" member object as we don't know if the function is to be used as a constructor. Object literals or objects created with Object.create() won't have it.

console.log(cat.prototype); //undefined

As for adding prototype member object to an object literal, a stack overflow question: Adding a prototype to an object literal