Array's has lots of helper functions, that is used all the time when developing js applications. It is super helpful to be able to manipulate an array like removing elements or adding elements at specific indexes. Another helpful function of arrays is to know where a specific item is in the array.

Objects can be used for representing data and it can help structure your code. An object can fx represent a user that has a firstname, surname, profile picture and a list of friends. It is constantly used in javascript and essential to learning the language.

Its warmup time!

• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/build-javascript-objects/
• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/accessing-object-properties-with-dot-notation/
• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/accessing-object-properties-with-bracket-notation/
• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/updating-object-properties/
• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/add-new-properties-to-a-javascript-object/
• https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/basic-javascript/using-objects-for-lookups/

Please add your freecodecamp username as answer for this exercise!

const numbersArray = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
const randomNumber = parseInt(Math.random() * 11);

// Write some code here

Copy the above code to your homework

1. Remove the item in numbersArray that is equal to randomNumber
2. Optional create a variable numbersToRemove. In a loop remove the number of items equal to numbersToRemove. Remember to have randomNumber inside of the forloop

Write a function where you speficy your speed in km/h and how far you have to go in km. The function has to return the time it will take to arrive at your destination. The time should be formatted like this: 3 hours and 34 minutes.

const speed = 50;
const destinationDistance = 432;
const travelTime = notThisFunctionName(speed, destinationDistance);
console.log(travelTime); // 4 hours and 42 minutes

const seriesDurations = [
  {
    title: 'Game of thrones',
    days: 3,
    hours: 1,
    minutes: 0,  
  },
  {
    title: 'Sopranos',
    days: 3,
    hours: 14,
    minutes: 0,
  },
  {
    title: 'The Wire',
    days: 2,
    hours: 12,
    minutes: 0,
  }
]

How much time of my life have i been watching series? Lets find out! Calculate how much time a series have taken as a percentage of an average lifespan of 80 years.

Firstly change the seriesDurations object to include your favorite series. Find the duration of a series here: http://tiii.me/

Using the seriesDurations log out the text:

Game of thrones took 0.01% of my life
Sopranos took 0.012% of my life
The Wire took 0.007% of my life

In total that is 0.2% of my life

Lets create some js where you can add songs from a list of available songs to your own list of songs you like.

const songDatabase = [{
    songId: 1,
    title: 'My baby',
    artist: 'Soggy socks',
  },
  {
    songId: 2,
    title: '3 nails in wood',
    artist: 'The carpenters',
  },
  {
    songId: 3,
    title: 'Blacker than black',
    artist: 'Instant coffee',
  },
  {
    songId: 4,
    title: 'When is enough too little?',
    artist: 'The spies girls',
  },
];

const myPlaylist = [];

In this task when i mention a song i mean an object that is represented as a song. You can also say that a song is represented as an object

Lets create a function that can add a song to the songDatabase array.

The function should be called addSongToDatabase and have one parameter called song. The type of song should be an object with the same keys as the songs in the songDatabase array.

Now add some of your favorite songs to the database using addSongToDatabase.

Now a question for you! Should this function return anything? What do you think, why/why not?

Create a function called getSongByTitle that returns the songs that match a song title. It has one parameter called title. It should return the song that match the title parameter.

Lets give an example:

const searchedSong = getSongByTitle('When is enough too little?');
console.log(searchedSong); // returns { songId: 4, title: 'When is enough too little', artist: 'The spies girls'}

const searchedSong2 = getSongByTitle('When is enough too');
console.log(searchedSong); // returns undefined

Try to use the function by searching for some different songs that are in the songDatabase and some that are not.

Hint: First find the index of the object in the songDatabase array where the title match, then return that index of the songDatabase array.

Optional: Add fuzzy search, so we can search for "When enough to little?" and still get the song with id 4.

Lets use the two functions we have created to make our own playlist! Create a new function called addSongToMyPlaylist it has a parameter called title.

Using the getSongByTitle and the addSong functions create a function where you specify the song title of the song you would like in your playlist!

Here is an example:

addSongToMyPlaylist('3 nails in wood');
console.log(myPlaylist); // [{ songId: 2, title: '3 nails in wood', artist: 'The carpenters' }]

Use this function to add some songs to your playlist!

What if there are multiple songs with the same name? Then we have problems in our getSongByTitle function! Instead of returning a song, return an array of songs that match the title parameter.

What if a user had multiple playlists? How could we accomodate that? Either describe how to fix this problem or make some code!

Smart-ease is going back to the basics. As always Smart-ease starts by helping people fix their problems. So lets venture out into the real world and see what we find:

You are sitting at a meeting. A person is presenting some interesting thought that you want to write down. You check your bag, but realise that you forgot to bring your notepad. Hmm you check the internet for an online solution. But you need to signup for them all, too bad... Maybe this could be a worthwhile problem so solve. Lets create a simple and easy to use notepad 📝

The first thing we will create is the functionality to save a note: Create a variable called notes and assign it to an empty array. Create a function called addNote. The addNote has two parameters:

• content parameter is a string.
• id is a number.

The addNote function shall push an object to the notes array. This object has two keys: content and id, that corresponds to the function parameters. The value of the keys should be the value of the corresponding parameters.

Now a user can add a note, but what if a user wants to see a specific note, but only remembers the id? Lets create that functionality for him: Create a function called getNoteFromId. The function has one parameter called id. When calling this function with an id it should return the relevant note object that corresponds to the id. If no id is specified or if the id is not a number, log out an error string. Hint: Use a for loop.

Should return an array of the notes.

Now a user can both add and get a note. What if the user just wants to read all his notes? Lets also create that functionality: Create a function logOutNotesFormatted. When calling the function it should log this string out for every note: "The note with id: 1, has the following note text: "some example note"."

Suddenly you get this great idea for making the note app even better!

Come up with a unique feature you think would make this app better. Write down the idea and see if you can implement it. If not dont worry :) If it is too hard to implement try and ask in the slack channel :)

Try an interactive version 💻 of your code here. Remember to insert your code in the top of the codepen :)

After a long day you come home to relax. The first thing you do is find your phone and start watching some youtube. Then check facebook, and then reading some news. Suddently a hour has passed. What happened to all that time you think to yourself. Maybe we can create some program to help with this problem! What if we could help users manage their smart phone usage?

Its going to work like this: A user can add smartphone activities. Then he can see a status on how his smartphone usage is going.

Lets create the first part of the functionality that is adding activities.

Create a variable called activities that stores all activities of the day. What type of variable would you think would make sense? Create a function called addActivity. It should have three parameters: date, activity and duration. The date should be a string, the activity a string and the duration a number. To save the activity push an object that contains the date, the activity and the duration to the activities variable.

Now a user can add an activity by writing:

addActivity('23/7-18', 'Youtube', 30);

/*
activities should now look like this
[{
    date: '23/7-18',
    activity: 'Youtube',
    duration: 30,
}]
*/

Just adding activities wont help the user very much, we need to add some functionality to show the user how his smart phone usage is going.

Create a function called showStatus. This function should use the activities variable and return a string saying the following: "You have added 3 activities. They amount to 78 min. of usage"

showStatus(activities); // will log out this "You have added 3 activities. They amount to 78 min. of usage"

Now what happens if we call showStatus and activities is empty? We need to take that into consideration: If activities is empty log out a string that says: "Add some activities before calling showStatus"

A user asks us if it is possible to set a limit for his smartphone usage. "Off course it is" we promptly reply! We need to store that limit somewhere, but where and what type should this be? So how should it work? When showStatus is called and the users usage is above the limit he set. Log out the following string: "You have reached your limit, no more smartphoning for you!"

Try and add some activities and call showStatus

Come up with one feature you think would be helpful for this program.

Optional

• Lets improve the addActivity, so that we dont need to specify the date, but the function automatically figures out what the date is. Check out this link: https://stackoverflow.com/a/34015511
• Improve the showStatus function by only showing the number of actitivies for that specific day.
• Create a function for calculating the activity a user has spent the most time on.

the Bonus homework for this week (for those of you want an extra challenge) do the following:

Go to http://roverjs.com/ and complete the functions and arrays chapters.

Go over your homework one last time:

• Does every file run without errors and with the correct results?
• Have you used const and let and avoided var?
• Do the variable, function and argument names you created follow the Naming Conventions?
• Is your code well-formatted (see Code Formatting)?

If you can answer yes to the above questions then you are ready to hand if the homework:

• Use the hyf-homework repo and add your homework files in the javascript/javascript1/week3 folder
• Make your commits for the homework. Remember to seperate the code into meaningful commits!
• Push the changes to github
• Share the github link to your classes slack channel.

🎉