Assignment 1.0.0 - Intro To Node!

• Assignment 1.0.0 - Intro To Node!
• Getting started
• Finishing
• Submitting On Time
• What's in an assignment?
  • From Scratch
  • Debug
  • Modify
  • Short Answers
• npm start vs npm test
  • playground.js
• Question 1: Create our files
• Question 2: Export a helloWorld function
• Question 3: Default Export greet
• Question 4: Import and export multiply
• Question 5: DEBUG
• Question 6: MODIFY
• Short answers
• Bonus: Review! ...and maybe nodemon

Welcome to your fist official JS assignment! It may not seem exciting to you, but we sure are pumped about it. We're going to start off simple, but you'll be amazed how quickly you'll be able to carry out complex tasks in the coming weeks.

To start off, let's explain how these assignments work.

Getting started

Whenever you get an assignment the first thing you should do is run

npm i
npm test

This will install any necessary dependencies and then show you all the tests you need to work on. We may explain each function in the README.md, but always run the tests because they are crucial to explaining what the code literally must do.

Finishing

In order to submit an assignment, you need to run your tests, commit your code, and then push it up to GitHub. So something like:

npm test
git add .
git commit -m "Finished!"
git push

Submitting On Time

You have to understand that "grades" don't exist at Marcy. We only need performance data in order to know how you're doing, and make sure the people who need help get it as quickly as they can. It's ok if you didn't finish by the deadline! Just show us what you have. We'll have office hours and reviews, and we want to know what you are all struggling with so we can use those meetings effectively. This is not about grades, its about seeing what you know, and where we can help!

What's in an assignment?

Some of homework will be a special case, but in general there will be 4 sections.

From Scratch

This is the bulk of the assignment. It's testing your ability to look at a blank page and create something. Usually, there will be a "from-scratch.js" file, but not always! Like in this assignment, you'll need to create your own files!

Debug

We'll be real with you: most of this job is fixing something broken. So in this part you'll be asked to try and get something working by mostly relying on reading tests.

This was 75% of my job, I cannot stress how important it is to get good at debugging.

-- Mike, Director of Marcy Curriculum

Modify

Given some existing code, can you enhance/change it? It's similar to debug in that there's existing code, but nothing is broken.

Short Answers

Your ability to communicate is just as important as your code. So we'll ask you to write a few sentences (think about the length of a long tweet) to answer a question. Read answers out loud to check flow, and use an external service to double check grammar.

To answer the questions, just edit each .md file in the short-answers folder under the # Answer section. Leave the # Feedback section blank, that's for your teacher!

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So those are the four sections. They may not be all in the assignment, but always check the README.md and run your tests to make sure you've done everything.

npm start vs npm test

Sometimes you'll want to play around and run files before testing directly. That's what node FILENAME or npm start commands are for. However, to make sure you got things right, use npm test or npm run test:w. Most of your assignments will have specific start commands for each section, but most of your labs will just use a single start command. The difference is that most projects have a single start, but our assignments are a lot more fine grained than that.

playground.js

You can also create what's called a "playground" (or "sandbox") file where you import any code you need, and then mess around with that file. We've included onehere so you can see it (and even added an npm script).

Alright! Let's get started with the actual assignment!

Question 1: Create our files

First up, you may have noticed our from-scratch test is expecting some files to exist, so let's make them! In the src folder please create the following files:

• index.js
• multiply.js
• greet.js

NOTE: This is a pretty important step! If you can't get the tests that check these files' existence to pass in 20 minutes, reach out to your teacher for help.

Question 2: Export a helloWorld function

Inside index.js write a function called helloWorld that RETURNS the string:

Hello world!

But that's not the hard part. The real challenge is: use a named export, to export the helloWorld function for our tests to read.

Question 3: Default Export greet

We've done a named export yes, but what about default exports? In greet.js, write a function called greet() that takes in a name argument and returns a string like:

greet('Jo')

Hello Jo, how are you?

Now, use a default export and export the function.

Question 4: Import and export multiply

Inside multiply.js write a function called multiply() that takes 2 numbers and RETURNS their product. Here's the tricky part:

• Default export the multiply() function from multiply.js
• Then require the multiply() function into your index.js
• Finally, add the multiply() function to the named exports of index.js

We exported a function out of its base file, imported it into an index file, and then re-exported it. Why? This pattern is called a Barrel File. Since index.js is a "magic" file in node, it can help clean up our exports.

See, if you just require a folder instead of a file, node will automatically check if theres an index.js file in the root of that folder, and then use that. Look how much this feature helps us:

// Doing this in a bunch of files:
const thing1 = require('./things/thing1');
const thing2 = require('./things/thing2');
const thing3 = require('./things/thing3');
const thing4 = require('./things/thing4');

// Is a lot more annoying than this
const { thing1, thing2, thing3, thing4 } = require('./things');
// Those are all exported from /things/index.js

This way, we get to write small, focused, well named files, and we only have to write all those requires once in an index. Barrel files aren't a good idea for most simple things like these assignments (just export multiple functions from a regular file), but they're a good trick to know for more complex projects.

Question 5: DEBUG

In debug.js We have a function called mirror() that's supposed to log and return whatever we pass into it. But the test is failing. What's wrong our code? Check out the tests in debug.spec.js and see if you can figure out what we're missing in debug.js.

Question 6: MODIFY

So we wrote a default export (not even using a named function) in modify.js. We did this because we thought it would only export one function. But now we've added anotherFunction(). So we have two things to do:

• rename the anonymous default export function as liarFunction()
• Export both anotherFunction() and liarFunction() as named exports.

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Short answers

Please answer all the short answers. They're on today's lecture, as well as a new article on "Semantic Versioning." If you're wondering why lectures and assignments look like #.#.#, that's what why! Though it's more an homage, our lessons aren't literally semantically versioned.

Bonus: Review! ...and maybe nodemon

It's day 1, so use this time to get ahead! This week we're going to review variables, data types, functions, string manipulation, and flow control. You learned all about these in the pre work, so go over your notes. Also you can take this time to experiment with Jest's watchAll mode with the npm test:w script.

If you really want something to do other than review JS, you can check out this article on nodemon. Nodemon (sounds like pokemon) automatically reruns files when they get saved. It's super handy. Also, tests will form the backbone of our assignments, so watch this video about getting started with Jest tests. Note, that is all about writing tests, but all you'll need to do is read tests, so just focus on understanding the ideas, more than the exact syntax.