Development Guide

Last updated: September 03, 2019

Intro

There are many ways to write JavaScript, and JavaScript is used for many different purposes from mobile apps to command line scripts and of course in the browser. This is a guide for how you can get started writing JS in an environment that will suit you well for this course and future projects you take on in JS.

Installing node

JavaScript was originally written to bring dynamic content to HTML and CSS websites. Node (Node.js) is a run-time compiler for running JS anywhere and everywhere (not just in the browser). Node Package Manager (npm) is the system which Node uses for installing dependencies (packages) for a program which let you take advantage of frameworks, functions, and tools other people have written. React and Express are popular examples of Node packages which we will become familiar with over the course of this semester.

To check if Node is installed, open the Terminal or Command Prompt app on your computer and run:

node -v

If something along the lines of v10.16.3 is returned, Node is set up successfully. If you have a version less than 8, consider installing a more recent release. If there is an error or no version is returned, follow the directions below.

To install Node, proceed to the node.js website and download the latest Long Term Support (LTS) version of Node. When the download has finished installing, open the file and follow the prompted instructions until Node is set up on your machine.

To assert everything installed correctly, run:

node -v

Picking a code editor

Few people write JS in full-fledged IDE's in the way you might be used to running Java in Eclipse or IntelliJ. Though there are solutions for this (like Webstorm) these often introduce overhead and unnecessary complexity.

Instead, JS devs often use lighter tools like VSCode, Atom, or Sublime Text. The CIS 197 staff tends to use VSCode because of the strong developer community, UI, and built-in terminal. All of these tools have built in package managers for installing packages which improve the developer experience like syntax highlighting, help formatting, and help with code completion.

Developing and testing JavaScript code

There are many ways to test JS code. For simple syntax checking, the easiest way is often via the developer tools in your browser (like Google Chrome) or by running the node command on its own in your terminal which gives you a Node-based JS REPL (type Ctrl + C to exit node).

To test a JS file, navigate in your terminal to the directory where the file is located (if you're not sure how to do this, find an intro guide on how to using your terminal online). From there, you can run node file-name. Any console.log statement executed in your file will print out to the console of your terminal. This is also a good way to check for syntax errors. It can also be useful to make a new file specifically for testing functions in another file. In the test file, you can require the primary file and call functions there.

Using a linter

A linter is a tool for checking that your JavaScript code both does not have syntax errors and is properly styled. In your homework assignments, you can see a .eslintrc file which specifies how to configure the linter to meet our preferred style guide for the course. You can learn more about ESLint here.

We recommend installing the ESLint package and related linter packages for your code editor of choice. Said packages will highlight issues with your code as you type so you can easily resolve them, much like a spell checker in Microsoft Word. You can also check for linter errors from your terminal via the eslint package found here. This is what we run when you submit your assignment to Gradescope.