Wrong output from annual interest program

Question

The output is the same as the number that is originally entered as input. I have no idea what I'm doing wrong here:

function main() {
//get the initial amount and the interest percentage
var amount = parseInt(readLine(),10);
var yearPercent = parseInt(readLine(),10);

var loan1 = new Loan(amount, yearPercent);

//output to console
console.log(loan1.yearIncome);
}

function Loan(amount, percent) {
this.amount = amount;
this.yearPercent = percent;
//your code goes here
this.yearIncome = amount;
var interestRate = new calcYearIncome(amount, percent);

};

function calcYearIncome(amount, percent){
//complete the function to calculate yearly income

interestRate = percent / 100;
this.yearIncome = interestRate * amount;

}

Answer 1

If you make an instance of the class Loan, like this:
var loan1 = new Loan(....
Then you can say "this" points to his owen object, in this case to loan1.

this.amount
means here
loan1.amount

Answer 2

Oh yes, I was starting with a language named Basic. In the 80's or 70's. And I needed years to bring these OOP things into my head 😂
Python is maybe better to start. But it's not type safe. And the switch to other languages may be harder.
At last it's a question of what you want to do with the programs.

Answer 3

Yes, I've always thought that OOP is difficult makes programming more difficult but it's funny that this is what we do everyday without thinking about it, in OOP a person is an object that has properties(hair) and values(black) but I think in the last challenge exercise it would have been helpful if the instructions mentioned that I would need to use the Return keyword to return the needed value back to the function, but I'm sure I would not have figured it out anyways because I was way off.

Answer 4

Have a look at this. And try to find out how it works:

function Loan(amount, percent) {
this.amount = amount;
this.yearPercent = percent;
//your code goes here
this.yearIncome = calcYearIncome;
};

function calcYearIncome(){
//complete the function to calculate yearly income
return this.amount *
this.yearPercent / 100;
}

Answer 5

Thank you, I think that the statement (this.yearIncome=calcYearIncome;) calls the function calcYearIncome and the returned value goes into the variable this.yearIncome which will later be displayed by:
console.log(loan1.yearIncome);

It's amazing how complicated this is, I first learned about functions with C++ and it would have been so easy to write a program like this using statements like cin for input and cout to display the results, including functions and return statements just for practice.

Answer 6

Is this statement here supposed to be considered a function?
console.log(loan1.yearIncome());

I'm referring to the last part yearIncome();
Here's the working code:
function main() {
//get the initial amount and the interest percentage
var amount = parseInt(readLine(),10);
var yearPercent = parseInt(readLine(),10);

var loan1 = new Loan(amount, yearPercent);

//output to console
console.log(loan1.yearIncome());
}

function Loan(amount, percent) {
this.amount = amount;
this.yearPercent = percent;
//your code goes here
this.yearIncome = calcYearIncome;

};

function calcYearIncome(){
//complete the function to calculate yearly income

return this.amount * this.yearPercent / 100;

}

Answer 7

Yes, I hate the JS methods too 😉

Answer 8

Great thanks, it seems like javascript is not a good language for people starting to learn programming, I started with the Basic programming language back in the early 90's, to jump within the code you had to use the goto statement, I'm guessing c++ and python are better for a beginner but I'm familiar with c++