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07-nodejs-setup.md

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Installing Node.JS

Node.JS is Javascript Runtime Environment for running JavaScript files directly on a computer. JavaScript is built into every web browser, but if you want to run JavaScript directly without a browser, you need to install Node.JS.

NOTE: We do not install Node.JS using the installer provided at the Node.JS website in this class. If you have this one installed, please uninstall it before proceeding with these instructions.

Node Version Manager (nvm)

Often as a developer, you will need to juggle multiple projects on our computer, each running a different version of Node.JS. Because of this, just installing a new version from the Node.JS website would be difficult and error-prone.

Luckily, there's a piece of open source software that can help called Node Version Manager, or nvm.

To install nvm, check out the nvm github page here:

nvm Github Page

Below the code, there is a README section. Usually when installing software from github you'll want to check the README for instructions. If you scroll down you'll see instructions for how to install nvm. In this case we can run a special command with curl to download and install nvm from the terminal.

So open a Terminal and use the curl command listed in the README. It should look something like this, although the version number in the URL might vary:

curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.37.2/install.sh | bash

When you do this you'll see something like this:

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 13527  100 13527    0     0  49731      0 --:--:-- --:--:-- --:--:-- 49915
=> Downloading nvm from git to '/home/your-user/.nvm'
=> Cloning into '/home/your-user/.nvm'...
remote: Enumerating objects: 333, done.
remote: Counting objects: 100% (333/333), done.
remote: Compressing objects: 100% (283/283), done.
remote: Total 333 (delta 38), reused 150 (delta 25), pack-reused 0
Receiving objects: 100% (333/333), 177.16 KiB | 1.46 MiB/s, done.
Resolving deltas: 100% (38/38), done.
=> Compressing and cleaning up git repository

=> Appending nvm source string to /home/your-user/.bashrc
=> Appending bash_completion source string to /home/your-user/.bashrc
=> Close and reopen your terminal to start using nvm or run the following to use it now:

export NVM_DIR="$HOME/.nvm"
[ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"  # This loads nvm
[ -s "$NVM_DIR/bash_completion" ] && \. "$NVM_DIR/bash_completion"  # This loads nvm bash_completion

The lines to pay attention to are the last three. These are the shell commands necessary to initialize nvm. But we don't want to have to run these commands everytime we open a terminal, so we should put these into our shell startup file

The general rule on this is:

If your shell is zsh, use ~/.zshrc If your shell is bash, use ~/.bashrc

You can determine which shell you have by typing echo $SHELL at the command line

You'll notice, in the example above, the nvm installer automatically added the lines to the ~/.bashrc even though the example runs zsh. You need to verify that the lines were correctly added to your startup file. Don't trust the installer to always do the right thing in this case. Everyone's system is different.

To verify it, open up your startup file in vscode with the code command. Use the appropriate startup filename depending on which shell you have (~/.zshrc or ~/.bashrc).

code ~/.zshrc

If you do not see the nvm startup lines in your file already, add them in there.

There are two ways to run your startup file. You can run it live in your current shell by typing the source command and following it with your startup file, or an even easier option is to just close your terminal window and open it back up.

Once you have done these steps, run nvm by itself at the command prompt. You should see the help messages from nvm. If this doesn't work, double check your shell startup files.

Installing Node.JS

Now that you have nvm installed and ready to go, you can use it to install a particular version of Node.JS.

Currently in this course, you will use version 16. While 14 and 12 should work as well, they are missing newer language features that you may like to use.

NOTE: Only stick to LTS versions of Node.JS. This stands for Long Term Support. These are the stable versions of Node.JS. The odd-numbered releases such as 15 are experimental releases, and should not be used for anything important. They are a way for people to test new releases of Node.JS, not something you should rely on for your code.

So let's install it!

nvm install 16

You should see something like this:

Downloading and installing node v16.14.0...
Downloading https://nodejs.org/dist/v16.14.0/node-v16.14.0-darwin-arm64.tar.xz...
######################################################################### 100.0%
Computing checksum with shasum -a 256
Checksums matched!
Now using node v16.14.0 (npm v8.3.1)
Creating default alias: default -> 16 (-> v16.14.0)

You'll notice we can just provide 16 here and not any specific version of Node.JS like 16.14.0. nvm is good like that, it will automatically install the latest version of 16.

Once this is complete, you should be able to type

node --version

and it should print out the correct version of Node.JS.

You can verify that the Node.JS you installed is coming from your nvm setup, by using this shell command:

which node

If it prints out a path with .nvm in it, then you've done it correctly!

/home/<<your username>>/.nvm/versions/node/v16.14.0/bin/node

Congratulations you've just installed Node.JS!

Mocha - One last step

You will use a tool called Mocha for testing your Javascript code. You will use it to test in your projects and also when you do assessments.

To install it, use the npm command.

NOTE: DO NOT confuse npm with nvm. They are different tools. nvm controls the version of Node.JS you have installed, while npm is responsible for installing Node Packages which are third party pieces of software written in JavaScript.

To install mocha, do this:

npm install -g mocha

The -g is called a flag. This changes the behavior of the install command.

In this case it means global. By default, npm will install files into your project directory. We want mocha to be installed for all projects, so we specify -g.

You can verify mocha works by typing

mocha --version

If it prints out a version number, pay yourself on the back, you have successfully installed Node.JS and Mocha!