We have learned Object-oriented programming and how class and inheritance work in JavaScript. Now, let's put what we have learned into practice.

We all know that keeping track of our incomes and expenses is crucial to staying on top of our budget, but doing it manually can be a tedious task. Well, in this lab, we're going to create a personal expense tracking program to help us with that! Our expense tracking program will help us automate the tedious task of categorizing our transactions into income and expenses, allowing us to take full control of our budget. But there's more! We won't just stop at recording our incomes and expenses. We will also add features that will make it even more useful, such as calculating the total income and expenses and the current balance. 💸

Let's get started!

• Fork this repo.
• Clone this repo.

• Upon completion, run the following commands:

git add .
git commit -m "Solved lab"
git push origin master

• Create a Pull Request and submit your assignment

This LAB is equipped with unit tests to provide automated feedback on your lab progress. In case you want to check the tests, they are in the tests/index.spec.js file.

To run the tests and your JavaScript code, open the SpecRunner.html file using the Live Server VSCode extension.

To see the outputs of the console.log in your JavaScript code, open the Console in the Developer Tools.

You will work on the src/index.js file.

Your task is to write the code in the src/index.js file following the below guidelines to make the tests pass. In this file, you will find the following starter code:

// Entry
class Entry {}

// Income
class Income {}

// Expense
class Expense {}

// Budget
class Budget {}

Let's have a look at the first test case together to get you started.

The first test case says that the Entry "should take 3 arguments: date, amount, and description". This means that the Entry class should have a constructor method that takes 3 arguments:

// Entry
class Entry {
  constructor(date, amount, description) {}
}

// Income
class Income {}

// Expense
class Expense {}

// Budget
class Budget {}

Implement the Entry class so that it has the following properties and methods:

• should take 3 arguments (date, amount, description).
• should take the date property as 1st argument and assign it to a property date.
• should take the amount property as 2nd argument and assign it to a property amount.
• should take the description property as 3rd argument and assign it to a property description.

• should be defined
• should receive 0 arguments
• should return the amount string with the amount and the € symbol (format: "AMOUNT €")

An Income object is an Entry with an additional property type by default set to "income".

Implement the Income class following the below guidelines. The Income class should inherit the properties and methods from Entry, which means that you have to use the extends keyword and the super() inside the constructor.

• Income should extend Entry.

• should take 3 arguments (date, amount, description).
• should take date as 1st argument and assign it to a property date.
• should take amount as 2nd argument and assign it to a property amount.
• should take description as 3rd argument and assign it to a property description.

This class is almost the same as the Income class, except that it has an additional property paid, and the type property has a default value of "expense".

An Expense is an Entry with an additional property type by default set to "expense". The Expense class instances should have an additional property paid used to keep track of whether the expense has been paid or not.

• Expense should extend Entry

• should take 4 arguments (date, amount, description, category)
• should take date as 1st argument and assign it to a property date.
• should take amount as 2nd argument and assign it to a property amount.
• should take description as 3rd argument and assign it to a property description.
• should take paid as 4th argument and assign it to a property paid.

This method needs to be re-implemented for Expense, because the Expense version is supposed to have a different return. It should return the amount string with a minus (-) sign. The requireme

• should be defined
• should receive 0 arguments
• should return the amount string with a minus sign, the amount, and the € symbol ("-AMOUNT €")

We are almost there! We are going to create a Budget class that will help us store our incomes and expenses and that way keep track of our budget. The Budget class should have the following properties and methods:

Add the following 4 methods to the Budget class:

• addEntry()
• getTotalIncome()
• getTotalExpense()
• getCurrentBalance()

When we first create a Budget, there should be no income or expenses. Therefore, the constructor should receive no arguments. Here is how the constructor should look like:

• should receive 0 arguments
• should create an entries property and assign it an empty array as the initial value

Adds 1 entry (income or expense) to the entries array. Here are the requirements for this method:

• should be defined
• should receive 1 argument (new entry that can be either an Income or an Expense object)
• should add the received entry to the entries array
• shouldn't return anything

Returns the total amount (number) of all incomes (entries with type of "income").

• should be a defined
• should take 0 arguments
• should return the sum (number) of all incomes
• should use the forEach() method to iterate over the entries array

Returns the total amount (number) of all expenses (entries with type of "expense").

• should be a defined
• should take 0 arguments
• should return the sum (number) of all expenses
• should use the forEach() method to iterate over the entries array

Returns the balance of the budget (total income - total expenses).

• should be defined
• should receive 0 arguments
• should return 0 if there are no entries.
• should calculate and return the balance, which is the total income minus the total expenses

As you may have noticed, methods getTotalIncome() and getTotalExpense() have a lot of repeated code. This makes them good candidates for refactoring.

Let's refactor them and fix this by implementing a new method getTotal(type) that will take the string type (either "income" or "expense") as an argument and return the total amount (number) of all entries with the given type.

Returns the total amount (number) of all entries with the given type.

• should be a defined
• should take 1 argument (a string with the type of entry)
• should return the total amount (number) of all entries with the given type
• should use the forEach() method to iterate over the entries array

Implement the getFormattedEntries() method that returns an array of strings with the formatted entries. The format of the string should be as follows:

• For incomes: "DATE | DESCRIPTION | +AMOUNT €"

• For expenses: "DATE | DESCRIPTION | -AMOUNT €"

Returns an array of strings with the formatted entries.

• should be a defined
• should take 0 arguments
• should return an array of strings with the formatted entries
• should use the forEach() method to iterate over the entries array

We have a real treat for you for the last bonus iteration! It is your turn to write the unit tests for the new methods getTotal() and getFormattedEntries() you just implemented. You should write the tests in the tests/bonus.spec.js file.

You should use the method requirement descriptions from the two previous iterations and the tests in the tests/index.spec.js file as guides to write the tests for the new methods. You got this! 💪

Happy Coding! 💙

class Dog {
  constructor (name) {
    this.name = name;
  }

  bark() {
    console.log(`${this.name} is barking.`);
  }
}

class Labradoodle extends Dog {
  constructor (name, color) {
    super(name);
    this.color = color;
  }
}

const dog1 = new Labradoodle("Daisy", "white");
dog1.bark();  // Output: "Daisy is barking."

array.forEach( function(element) {
  // code to be executed for each element
});

const fruits = ['apple', 'banana', 'cherry'];

fruits.forEach( function(element, index) {
  console.log(`${index}: ${element}`);
});

fruits.forEach((element, index) => {
  console.log(`${index}: ${element}`);
});

git add .
git commit -m "Your commit message"
git push

git remote -v