Object being recognized as null or undefined

All credit goes to @JaromandaX. He explained the issue in the comments of the question.

Even though functions are Objects in JavaScript they are NOT identical. To access the prototype of a function function() {}.prototype can be used. But in the question, it is trying to access the prototype of a regular object, not a function object, which is undefined, thus the error.

Object.assign(House.__proto__, housePrototype); 

With this it is possible to assign desired object to the prototype (It is not recommended to assign any variables to proto and it si not at all a common pra)

The solution code would be

const House = {
    name: 'houseObject',
     readLocation: (location)=>{
      console.log(`house is located at ${location}`)
    }
  }

  const housePrototype = {
    readLocation: (location) => {
    console.log(`house prototype is located at ${location}`)
    }
  }

  Object.assign(House.__proto__, housePrototype)
  
  House.readLocation('Malabe');

I found a complete description in following StackOverflow thread __proto__ VS. prototype in JavaScript

Hey Bro the problem is House.prototpe because the object house has no object called prototype there are only two name and readLocation so change code to this : from this :

const House = {
    name: 'houseObject',
     readLocation: (location)=>{
      console.log(`house is located at ${location}`)
    }
  }

  const housePrototype = {
    readLocation: (location) => {
    console.log(`house prototype is located at ${location}`)
    }
  }

  Object.assign(House.prototype, housePrototype)
  
  House.readLocation('Malabe');
  console.log(House);

to this :

const House = {
    name: 'houseObject',
     readLocation: (location)=>{
      console.log(`house is located at ${location}`)
    }
  }

  const housePrototype = {
    readLocation: (location) => {
    console.log(`house prototype is located at ${location}`)
    }
  }

  Object.assign(House, housePrototype)
  
  House.readLocation('Malabe');
  console.log(House);

Usefull docs: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign#try_it

const House = {
  name: 'houseObject',
  readLocation: (location)=>{
    console.log(`house is located at ${location}`)
  }
}

const housePrototype = {
  readLocation: (location) => {
    console.log(`house prototype is located at ${location}`)
  }
}

//Object.assign(target, src);
Object.assign(House, housePrototype);

House.readLocation('Malabe');
console.log(House);