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

Kathleen Stearns
Kathleen Stearns
1,318 Points
Posted by Kathleen Stearns
Kathleen Stearns
1,318 Points

What am I missing?

I've entered in what I thought was the correct code, and got a syntax error that after (this) the firstName, lastName wasn't needed. When I took it out it said that it was needed. Clearly I'm missing something else, what is it?

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

Person.prototype.fullName = function() {
 return this.firstName + " " + this.lastName; 
};
teacher.js 
function Teacher(firstName, lastName, roomNumber) {
  Person.call(this, firstName, lastName);
  this.firstName = firstName;
  this.lastName = lastName;
  this.room = roomNumber;
}
Colton Ehrman
Colton Ehrman
Courses Plus Student 5,859 Points

When you do

Person.call(this, firstName, lastName)

it will automatically setup 

this.firstName = firstName and this.lastName = lastName

2 Answers

Maja B.
Maja B.
12,984 Points
Maja B.
Maja B.
12,984 Points

I think you should take

this.firstName = firstName;
this.lastName = lastName;

out of Teacher constructor.

But inside of a Person constructor they should stay.

kheiferfuller
kheiferfuller
8,635 Points
kheiferfuller
kheiferfuller
8,635 Points

Your code is technically correct but try to think of it in terms of DRY coding. You're restating the function in there. When you call 

Person.call(this, firstName, lastName);

You're running your code through the Person.js which already contains

this.firstName = firstName;
 this.lastName = lastName;

so the editor is seeing that you've both of them and is getting a little peeved, I think. I'm not sure where your error was exactly. But based on your current code, if you were to rewrite your code to demonstrate that you understand the call function as below, it should work just fine.

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