README.md

Homework Javascript Week 3

The homework for this week can be found in the homework folder.

Exercises

Starter code for all exercises is located in the homework folder. Modify the starter code so that the requirements of the exercise are met. At the bottom of each exercise file you will see a code snippet similar to:

// Do not change or remove the code below
module.exports = giveCompliment;

Do not delete or modify that code. It is required for automatic testing of the exercise.

Exercise 1: You are amazing

File: ex1-giveCompliment.js

1. Complete the function named giveComplimentas follows:

   • It should take a single argument: name.
   • Its function body should include a variable that holds an array, compliments, initialized with 10 strings. Each string should be a compliment, like "great", "awesome" and so on.
   • It should randomly select a compliment from the array.
   • It should return the string "You are compliment, name!", where compliment is a randomly selected compliment and name is the name that was passed as the function's argument.

2. Call the function three times, giving each function call the same argument: your name. Use console.log each time to display the return value of the giveCompliment function to the console.

Exercise 2: Dog years

File: ex2-dogYears.js

You know how old your dog is in human years, but what about dog years? Let's calculate it!

1. Complete the function named calculateDogAge.

   • It takes one argument: your (fictional) puppy's age (number).
   • Calculate your dog's age based on the conversion rate of 1 human year to 7 dog years.
   • Return a string: "Your doggie is age years old in dog years!"

2. Use console.log to display the result of the function for three different ages.

Exercise 3: Be your own fortune teller

File: ex3-tellFortune.js

Why pay a fortune teller when you can just program your fortune yourself?

1. Create four arrays, numKids, partnerNames, locations and jobTitles. Give each array five random values that have to do with the name of the variable.

2. Complete the function selectRandomly. This function should take an array as a parameter and return a randomly selected element as its return value.

3. Complete the function named tellFortune as follows:

   • It should take four arguments: number of children (number), partner's name (string), geographic location (string) and job title (string).
   • It should use the selectRandomly function to randomly select values from the arrays.
   • It should return a string: "You will be a jobTitle in location, married to partnerName with numKids kids."

4. Call the function three times, passing the arrays as arguments. Use console.log to display the results.

Note: The DRY principle is put into practice here: instead of repeating the code to randomly select array elements four times inside the tellFortune function body, this code is now written once only in a separated function.

Exercise 4: Shopping at the supermarket

File: ex4-shoppingCart.js

Let's do some grocery shopping! We're going to get some things to cook dinner with. However, you like to spend money and always buy too many things. So when you have more than 3 items in your shopping cart the first item gets taken out.

1. Create an array called shoppingCart that holds the following strings: "bananas" and "milk".

2. Complete the function named addToShoppingCart as follows:

   • It should take one argument: a grocery item (string)
   • It should add the grocery item to shoppingCart. If the number of items is more than three remove the first one in the array.
   • It should iterate through the array in order to list out the items in the shopping cart.
   • It should return a string: "You bought shoppingCart!".

3. Call the function three times, each time with a different string as the argument. Use console.log to display the results.

Exercise 5: Improved shopping at the supermarket

File: ex5-shoppingCartRedux.js

From a best practice point of view, there is a big problem with the code of the previous exercise (4): it modifies ("mutates") a global variable. In larger code bases this can become problematic, as it will be difficult to track down places in the code that might also (unexpectedly) mutate the global variable and, by doing so, cause bugs.

A function that mutates a global variable or in some other way interacts with the "outside world" (e.g. accessing a database, making a network request, or even logging something to the console) is said to cause "side effects. Sometimes this is necessary. A program that does not in some way interact with the outside world cannot possibly do something useful. However, in all other cases side-effects must be avoided.

Experienced developers prefer to work with pure functions. These functions do not access (let alone, mutate) any data that exists outside of their own scope and return results solely through the function's return value. All required data should be passed through the argument list.

A key characteristic of a pure function is that if it is repeatedly called with the same argument it always produces the same result. This is clearly not the case with the addToShoppingCart() function of the previous exercise.

In the current exercise we will rewrite the addToShoppingCart function to make it pure. Do the following:

1. Complete the parameter list of addToShopping(). As a first parameter it should accept a shopping cart array and as a second parameter it should accept a grocery item to be added.
2. The function should return a new shopping cart array, following the same rule as in the previous exercise: it should contain a maximum of three items.
3. The shopping cart passed as an argument should not be modified.
4. When constructing the new shopping cart array you should make use of the ES5 spread syntax.
   See also Spread syntax (...) on MDN Web Docs.

Exercise 6: Total cost is

File: ex6-totalCost.js

You want to buy a couple of things from the supermarket to prepare for a party. After scanning all the items the cashier wants to give you the total price, but the machine is broken! Let's write her a function that does it for her instead!

1. Create an object named cartForParty with five properties. Each property should be a grocery item (like beers or chips) and hold a number value (like 1.75 or 0.99).

2. Write a function called calculateTotalPrice.

   • It takes one argument: an object that contains properties that only contain number values.
   • Loop through the object and add all the number values together.
   • Return a string: "Total: €amount".

3. Call the function once, giving it the object cartForParty as an argument. Use console.log to display the result.

Exercise 7: Mind the privacy

File: ex7-mindPrivacy.js

Look at the following data maintained by the HR department:

const employeeRecords = [
  {
    name: 'John',
    occupation: 'developer',
    gender: 'M',
    email: '[email protected]',
    salary: 50000,
  },
  {
    name: 'Jane',
    occupation: 'manager',
    gender: 'F',
    email: '[email protected]',
    salary: 60000,
  },
];

Sometimes it is necessary for the HR department to share employee records with other departments. However, it should respect the privacy of the employees and never give out data that is considered private. Usually, salary is considered private and let's for the sake of argument also consider gender private. So when the HR department sends out the data it should create a new array with objects that just contains the name, occupation and email properties.

You should do the following:

1. Complete the filterPrivateData() function. It should take a single argument: the array of employee records.
2. It should create a new array, containing employee data without the private data.
3. Use object destructuring to extract the non-private properties from an employee record (an object) and object literal shorthand to create a new employee record with just the non-private parts (name, occupation and email).
4. Return the new array as the return value of the function.