LAB | JS Vikings

Learning Goals

This exercise allows you to practice and apply the concepts and techniques taught in class.

Upon completion of this exercise, you will be able to:

• Run predefined tests in Jasmine to verify that the program meets the technical requirements.
• Identify expected code behavior by reading and understanding test results and errors.
• Define a class and use it to create objects (instances).
• Create a subclass that extends a parent class using extends and super() to inherit properties and methods.
• Define class methods that use the this keyword to access object properties.
• Add or remove items from an array using the array methods (push, pop, shift, unshift, and splice).
• Iterate over arrays using the for and forEach loops.
• Pass values as arguments to functions.
• Use the return keyword to return a value from a function.

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Introduction

We have learned Object-oriented programming and how class and inheritance work in JavaScript. Now let's work with our Viking friends, applying the concepts we have just learned.

Requirements

• Fork this repo.
• Clone this repo.

Submission

• 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

Test Your Code

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/viking.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.

Instructions

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

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

// Soldier
class Soldier {}

// Viking
class Viking {}

// Saxon
class Saxon {}

// War
class War {}

Iteration 0: First test

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

The first test case says that "Soldier class >> should receive 2 arguments (health & strength)", so we have to write the correct code to pass this test. Let's make the Soldier class receive two arguments:

// Soldier
class Soldier {
  constructor(health, strength) {}
}

// Viking
class Viking {}

// Saxon
class Saxon {}

// War
class War {}

Iteration 1: Soldier

Modify the Soldier class and add 2 methods to it: attack(), and receiveDamage().

class

• should receive 2 arguments (health & strength)
• should receive the health property as its 1st argument
• should receive the strength property as its 2nd argument

attack() method

• should be a function
• should receive 0 arguments
• should return the strength property of the Soldier

receiveDamage() method

• should be a function
• should receive 1 argument (the damage)
• should remove the received damage from the health property
• shouldn't return anything

Iteration 2: Viking

A Viking is a Soldier with an additional property, their name. They also have a different receiveDamage() method and a new method, battleCry().

Modify the Viking class, have it inherit from Soldier, re-implement the receiveDamage() method for Viking, and add a new battleCry() method.

inheritance

• Viking should extend Soldier

class

• should receive 3 arguments (name, health & strength)
• should receive the name property as its 1st argument
• should receive the health property as its 2nd argument
• should receive the strength property as its 3rd argument

attack() method

(This method should be inherited from Soldier, no need to re-implement it.)

• should be a function
• should receive 0 arguments
• should return the strength property of the Viking

receiveDamage() method

This method needs to be re-implemented for Viking because the Viking version needs to have different return values.

• should be a function
• should receive 1 argument (the damage)
• should remove the received damage from the health property
• if the Viking is still alive, it should return "NAME has received DAMAGE points of damage"
• if the Viking dies, it should return "NAME has died in act of combat"

battleCry() method

Learn more about battle cries.

• should be a function
• should receive 0 arguments
• should return "Odin Owns You All!"

Iteration 3: Saxon

A Saxon is a weaker kind of Soldier. Unlike a Viking, a Saxon has no name. Their receiveDamage() method will also be different than the original Soldier version.

Modify the Saxon, constructor function, have it inherit from Soldier and re-implement the receiveDamage() method for Saxon.

inheritance

• Saxon should extend Soldier

class

• You don't have to include a constructor method since this class will inherit perfectly from the parents class, both the health and the strength (it extends Soldier class 😉 )

attack() method

This method should be inherited from Soldier, no need to re-implement it.

• should be a function
• should receive 0 arguments
• should return the strength property of the Saxon

receiveDamage() method

This method needs to be re-implemented for Saxon because the Saxon version needs to have different return values.

• should be a function
• should receive 1 argument (the damage)
• should remove the received damage from the health property
• if the Saxon is still alive, it should return "A Saxon has received DAMAGE points of damage"
• if the Saxon dies, it should return "A Saxon has died in combat"

BONUS - Iteration 4: War

Now we get to the good stuff: WAR! Our War class will allow us to have a Viking army and a Saxon army that battle each other.

Modify the War class and add 5 methods to its class:

• addViking()
• addSaxon()
• vikingAttack()
• saxonAttack()
• showStatus()

class

When we first create a War, the armies should be empty. We will add soldiers to the armies later.

• should receive 0 arguments
• should assign an empty array to the vikingArmy property
• should assign an empty array to the saxonArmy property

addViking() method

Adds 1 Viking to the vikingArmy. If you want a 10 Viking army, you need to call this 10 times.

• should be a function
• should receive 1 argument (a Viking object)
• should add the received Viking to the army
• shouldn't return anything

addSaxon() method

The Saxon version of addViking().

• should be a function
• should receive 1 argument (a Saxon object)
• should add the received Saxon to the army
• shouldn't return anything

vikingAttack() method

A Saxon (chosen at random) has their receiveDamage() method called with the damage equal to the strength of a Viking (also chosen at random). This should only perform a single attack and the Saxon doesn't get to attack back.

• should be a function
• should receive 0 arguments
• should make a Saxon receiveDamage() equal to the strength of a Viking
• should remove dead Saxons from the army
• should return result of calling receiveDamage() of a Saxon with the strength of a Viking

saxonAttack() method

The Saxon version of vikingAttack(). A Viking receives damage equal to the strength of a Saxon.

• should be a function
• should receive 0 arguments
• should make a Viking receiveDamage() equal to the strength of a Saxon
• should remove dead Vikings from the army
• should return result of calling receiveDamage() of a Viking with the strength of a Saxon

BONUS - Iteration 5

Since there is a lot of repetitive code in the previous two iterations, methods vikingAttack() and saxonAttack(), try to create one generic method and call it in the case of vikingAttack and in the case of saxonAttack instead of using almost the same code for both methods. (This iteration doesn't have the test, so ask your TAs and your instructor to give you feedback on the quality of your code after the refactor.)

showStatus() method

Returns the current status of the War based on the size of the armies.

• should be a function
• should receive 0 arguments
• if the Saxon array is empty, should return "Vikings have won the war of the century!"
• if the Viking array is empty, should return "Saxons have fought for their lives and survived another day..."
• if there are at least 1 Viking and 1 Saxon, should return "Vikings and Saxons are still in the thick of battle."

Happy Coding! ❤️

FAQs

I am stuck in the exercise and don't know how to solve the problem or where to start.

If you are stuck in your code and don't know how to solve the problem or where to start, you should take a step back and try to form a clear question about the specific issue you are facing. This will help you narrow down the problem and come up with potential solutions.

For example, is it a concept that you don't understand, or are you receiving an error message that you don't know how to fix? It is usually helpful to try to state the problem as clearly as possible, including any error messages you are receiving. This can help you communicate the issue to others and potentially get help from classmates or online resources.

Once you have a clear understanding of the problem, you will be able to start working toward the solution.

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All of the Jasmine tests are failing and in red. Why did this happen?

One possible reason why all of the Jasmine tests are failing is that there is a syntax error in the code being tested. If the code contains a syntax error, it will not be loaded properly and none of the tests will be able to run. This will cause all of the tests to fail.

To troubleshoot this issue, you will need to examine the code being tested for syntax errors. Look for missing brackets, semicolons, or other syntax issues that could be causing the problem. If you find a syntax error, correct it and try running the tests again.

Another possibility is that there is an issue with the tests. It is possible that you may have modified the test file and caused an issue. If you have made changes to the test file, try copying and pasting the original test file and running the tests again to see if this resolves the issue.

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How do I loop over an array using the forEach() method?

The forEach() method executes a provided function once for each array element. It does not return a new array but rather executes the function on each element in the array.

The syntax of the forEach() method is as follows:

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

Here is an example that uses the forEach() method to log each element and its index in an array to the console:

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

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

You can also use an arrow function as the callback function for forEach():

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

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How do I remove an element from an array?

You should use the splice() method to remove an array element at a specified index. The splice() method modifies the original array and returns an array containing the removed elements.

Syntax:

array.splice(start, deleteCount, item1, item2, ... )

• start: The index of the first element to be removed.
• deleteCount: The number of elements to be removed.
• item1, item2, ...: (optional) The elements to add to the array, starting at the start index.

For example, to remove an array element at index 2 (which is "c"):

let numbers = ["a", "b", "c", "d", "e"];

// Remove 1 element starting at index 2 (removes "c")
let removed = numbers.splice(2, 1);

console.log(numbers);  // Output: ["a", "b", "d", "e"]
console.log(removed);  // Output: ["c"]

For more information, check: MDN: splice()

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How can I extend a class and reuse methods through inheritance?

In JavaScript, you can use the extends keyword to create a subclass that extends a superclass (also called a base class).

The subclass inherits methods and properties from the superclass and can also have its own methods and properties.

Here is an example of extending a class and reusing its methods in JavaScript:

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."

In this example, the Labradoodle class extends the Dog class and inherits the name property and the bark() method. The Labradoodle class also defines its own property color.

When the bark() method is called on the dog1 object, it uses the method bark() coming from the Dog class, because the Labradoodle class extends the Dog class and inherits its methods and properties.

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I am unable to push changes to the repository. What should I do?

There are a couple of possible reasons why you may be unable to push changes to a Git repository:

1. You have not committed your changes: Before you can push your changes to the repository, you need to commit them using the git commit command. Make sure you have committed your changes and try pushing again. To do this, run the following terminal commands from the project folder:

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

2. You do not have permission to push to the repository: If you have cloned the repository directly from the main Ironhack repository without making a Fork first, you do not have write access to the repository. To check which remote repository you have cloned, run the following terminal command from the project folder:

git remote -v

If the link shown is the same as the main Ironhack repository, you will need to fork the repository to your GitHub account first and then clone your fork to your local machine to be able to push the changes.

Note: You should make a copy of your local code to avoid losing it in the process.

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