Development setup

Code Editor

You can choose any editor you want VS Code, WebStorm IDE, Sublime Text or even Vim.

We recommend using VS Code. Install VS Code.

Creating a File

  1. Launch VS Code. Type code in command line interface prompt or search bar (the most common CLI commands).

Pro tip: In the terminal, you can simply type code . to launch VS Code in the current folder. To set up this terminal shortcut in macOS, open up VS Code, and use cmd + shift + p to open Search. Type in shell, and install the 'code' command.

  1. Use your code editor to write some JavaScript code. Type the following:

    a = 'hello'
  2. Save your file as test.js in any folder you decide.

Running JavaScript Code On Computer

Now that you have your code, you need to run it with a program called node.js.

  1. Download the latest stable version of node.js, a program to run JavaScript. If you're using Windows install Windows Subsystem for Linux first and follow instructions for Linux from now on.

    1. For companies that use node, the best practice is to use nvm to install node.js.
    2. Install nvm.
    3. use nvm to install node version 14 by typing into your terminal: nvm i 14.

    Installing NodeJS on ChromeBook.

  2. Open your terminal and use cd to go to the folder that contains your file.

  3. Run your file using node: node test.js.

  4. You should see the output hello.

Browser-based setup

If you don't want to install node locally you use run javascript code in your browser. Go to GitPod. You'll be asked to create an account or you can also login using a Github account.

Running HTML Code on the Browser

Sometimes, you want to test something really quick and you are simply too lazy to create a new file. You can also write some quick code on the browser and immediately run it.

  1. Open your browser, then right-click on the browser, then click on Inspect Element or Inspect (Firefox and Chrome).
  1. In the screen that appears, click on the Console tab:
  1. After that, you can start typing code! For now, type console.log("hello"). And then type enter key.

  2. To write code on multiple lines, you must type Shift + Enter (only Enter for Windows).

Alternatively, you can run node directly from terminal. Type node to start node REPL (read–eval–print loop).

Running HTML Code from VS Code

Once you have completed writing and saving your HTML code on a file name xxxx.html, you are ready to run the html code on a browser. The easiest way is to run it directly from VS Code. However, before you can run the html code, you will need to install the open in browser extension by techER.

Launch VS Code.

For Mac users: Click on CodePreferencesExtensions. Or use [shift] + [command] + [x] keys.

For window users: Click on FilePreferencesExtensions. Or use [Ctrl] + [Shift] + [X] keys.

Enter open in browser in search box, and then select open in browser by techER. Install the extension.

While you are in VS Code, edit your html file. For window users, right click and select View in Browser. For Mac users, press [control] key and click and select Open in Default Browser, or press [option]+[B] keys.

Your default browser will be launched with your html file running.

Submitting Challenges

You can skip this section and come back when you finish JS 0 - Foundations.

Create an account on if you don't already have one.

For most of the steps below, you will be typing the commands into the terminal.

These steps are the same set of instructions you will most likely follow at work. Each challenge you solve is simulating building a feature at work.

If this is all new to you, these steps may seem very intimidating. When you start a new job, you will be equally intimidated because of all the specific tools each company uses. It is important to ask questions when you feel overwhelmed, there will be people on the chatroom help answer your questions.

Local Setup

When you join a software engineering company, the first step is setting up your machine, downloading the codebase, and setting up the codebase. (video instructions)

  1. After installing node, install c0d3 CLI (used to submit challenges): npm i -g c0d3.

    If you run into a Missing write access ... EACCES error, you need to run npm with sudo: sudo npm i -g c0d3.

  2. Install git and familiarize yourself with common git commands.

  3. Install yarn by running npm install -g yarn.

  4. Use git to clone the curriculum into your machine: git clone

  5. Go into the curriculum root folder by typing cd curriculum.

  6. Download the necessary libraries by running yarn install.

Browser Setup

Alternatively, you can submit challenges straight from your browser.

  1. Go to GitPod. You'll be asked to create an account or you can also login using a Github account.
  2. After your workspace is created, you'll have most of the tools you need at your disposal (git, node, npm and yarn). You'll need to install only the c0d3 CLI tool used to submit the challenges, by typing npm i -g c0d3 on the terminal at the bottom of the screen. Note: every time your workspace is restarted you'll need to run this command again.
  3. After installing the CLI tool, type c0d3 login and enter your C0D3 account credentials to be able to submit the challenges.
  4. Now the only thing remaining is to download the necessary libraries by running yarn install.

Solving Challenges

git status is your best friend. It tells you what branch you are currently on and which files are changed and/or staged for commit.

Solving each challenge is like building a feature at work. You must always checkout checkout master before creating a new branch to work on a new feature.

Branch names: Usually branch names are for your own eyes only, so you do not have create branches with meaningful names.

Note: Except for steps 3 (reading the challenge) and 4 (open and editing the file), all the commands should be run in the terminal

  1. Make sure you are on the master branch: git checkout master.

  2. Create a new branch from master (pro tip: p1 for problem 1): git checkout -b p1.

  3. Go to, click on Curriculum, select lesson 0, and read challenge 1.

  4. Write the solution by opening, editing, and saving js0/1.js (means file 1.js inside folder js0).

  5. Test your file by running npm run test. (Make sure tests are passing 100%) You will have to type q or CTRL c to get out of the test script.

  6. Add and commit changed files. Do not commit package-lock.json file.

    • git add js0/1.js → stages the file to be saved.

    • git commit -m "solves problem 1" → saves the changes.

      If you forget to put -m, you will be put into vim. To get out, type :wq to save and exit.

      The commit message (the text that comes after -m) should be present tense and describe what the change does.

      If you do git status and see changes to the file package-lock.json or yarn-lock.json, you would also commit these changes at work. These files lock in the version of the libraries used to run your files. However, to make reviews for your submission easier, do not commit changes to these files.

  7. Submit your solution: c0d3 submit

    • Note: You will be prompted to choose the exact lesson and challenge you are currently submitting. You should select lesson 0 and problem 1.
    • Go back to your student page ( → Curriculum → lesson 0), refresh it, and see the solution you just submitted!
  8. Go back to step 1 and repeat for the next challenge.

Make sure you go back to STEP 1 and run git checkout master so you are on master branch before creating a new branch so you can start the next problem fresh. If you don't then you will be creating a new branch from existing branch and all your solutions will be piled up together.

If you accidentally made a commit to your master branch, you need to undo the commit.

  1. Undo the last commit: git reset HEAD~.
  2. Go to the branch for your problem (we will use p1 as an example):
    • If the branch does not exist, you need to create one: git checkout -b p1.
    • If the branch exists, you can just switch to it (by omitting the -b option): git checkout p1.
  3. Continue with step 6 and onwards (add and commit).

Getting Feedback

As a software engineer, after submitting a feature you will wait for other software engineers to review your code.

Similarly, after submitting your solution, your solution will be reviewed by other engineers to make sure you are following best practices in your code.

You should be able to see your submissions when you go to the Curriculum and selecting a lesson.

It can take some time for a mentor to review your code. Feel free to go to JS0-Foundations chatroom to request a review.

If your code is not following best practices, your submission will get rejected. The following steps will help you resubmit.

Example: Problem 5 is rejected.

  1. Go to the branch that has the commit for problem 5: git checkout p5 (if your branch was called p5).
  2. Open and edit the file js0/5.js and address the comment you received.
  3. Add and commit changed files:
    • git add js0/5.js → stages the file to be saved
    • git commit -m "fixes problem 5 suggestion" → saves the changes
  4. Submit your solution again: c0d3 submit.

Completing your submission

As a software engineer, you need to merge your code back into your master branch after the code has been approved.

When all of your submissions have been approved, you need to follow these steps (video instructions):

  1. Go to the master branch: git checkout master.
    • If you have done this correctly, you will notice that all of the your solutions are missing. This is because your solutions are on different branches and we need to merge them in.
  2. Merge your branch containing the solution to problem 1 (we will use p1 as example) into your existing (master) branch:
    • git merge p1.
    • By doing this, master branch will now have your solution to challenge 1.
  3. Merge your branch containing problem 2 solution (we will be using p2 as an example) into your existing (master) branch:
    • git merge p2.
    • By doing this, master branch will now have your solution to challenge 2.
  4. Continue merging the remaining branches into master.
    • At this point, master should have all the approved solutions to all the challenges in this lesson.

To check if you did everything correctly go to p1 (or any other challenge branch) and type git diff master. It should not print anything, meaning there is no difference between your branch and master.

Reusing your branches

  1. Go to an existing branch that you plan to use for problem 1 (e.g. p1)
    • git checkout p1
      • (Notice how we did not add a -b flag because we are not creating a new branch)
  2. Update this branch with all the code in master: git merge master
  3. Write the solution by opening and editing js1/1.js
  4. Test your file by running npm run test (make sure tests are passing 100%)
  5. Add and commit changed files
    • git add js1/1.js
    • git commit -m "solves problem 1" → saves the changes
      • If you forget to put -m, you will be put into vim. To get out, type :wq to save and exit.
    • c0d3 submit to upload your work to for code review
  6. Start from step 1 and repeat for the next challenge

Next Step

Congratulations! You have written your first JavaScript program and you know how to run code directly in the browser. Now you are ready to start your journey.

JS 0 - Foundations

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