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JavaScript Object-Oriented JavaScript (2015) Prototypal Inheritance Setting Up the Prototype Chain

Kristen Thayer
Kristen Thayer
5,501 Points
Posted by Kristen Thayer
Kristen Thayer
5,501 Points

'You're missing the "Person.call"'... except I'm not.

This is my code, but I keep getting an error message... any ideas?

function Teacher(firstName, lastName, roomNumber) { Person.call(this, firstName, lastName); this.room = roomNumber; }

person.js 
function Person(firstName, lastName) {
  this.firstName = firstName;
  this.lastName = lastName;
}

Person.prototype.fullName = function() {
 return this.firstName + " " + this.lastName; 
};

function Teacher(firstName, lastName, roomNumber) {
  Person.call(this, firstName, lastName);
  this.room = roomNumber;
}
teacher.js 
function Teacher(firstName, lastName, roomNumber) {
  this.firstName = firstName;
  this.lastName = lastName;
  this.room = roomNumber;
}

2 Answers

Jason Anders
MOD
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Hey Kristen.

First off, for this challenge it's important to know that the person.js file does not get altered or added to at all, so all the code you will write will be only in the teacher.js file. So, delete any code you added to the `person.js' file.

So in the teacher.js file, you are on the right track, but you don't need to 're-declare' the firstName and lastName variables as this is done in the Person construct. You will only need to declare the unique variable for the Teacher. So, for the first part of the challenge, you are to call the Person constructor in the Teacher constructor like so

function Teacher(firstName, lastName, roomNumber) {
  Person.call(this, firstName, lastName);
  this.room = roomNumber;
}

For the second part of the challenge, you just need to add the line of code so that the Teacher can inherit from the Person successfully. 

function Teacher(firstName, lastName, roomNumber) {
  Person.call(this, firstName, lastName);
  this.room = roomNumber;
}

Teacher.prototype = Object.create(Person.prototype);

It's been quite some time since I've done JavaScript, so I may not have the most clear explanation, but Andrew does a really good job of it in the video just prior to this challenge starting at about 2:30.

Hope this helps some. Keep Coding! :)

Kristen Thayer
Kristen Thayer
5,501 Points
Kristen Thayer
Kristen Thayer
5,501 Points

Thanks! I've got it now :)