Popcode is a simple HTML/CSS/JavaScript editing environment for use in the classroom. It's a lot like JSBin, JSFiddle, or CodePen, but it focuses on giving specific, immediate, human-friendly feedback when the code contains errors.

Popcode is the official editing environment for the Code Nation Intro to Web Development program in the 2019–2020 school year.

You can try out Popcode at https://popcode.org.

• Features
  • About validation
  • Feature roadmap
• Technical details
  • Architecture Overview
• Contributing
  • Running locally
  • Debug Mode
  • Developer Reference
• License
• Contributors
• Thanks to
• Contact

• Edit HTML, CSS, and JavaScript in the browser; in-browser preview updates as you type.
• Get immediate, comprehensive, easy-to-understand feedback about problems in your code.
• Errors can't be ignored. If there are any errors in the code, the live preview is replaced by an error list.
• JavaScript runtime errors are also reported in human-friendly language, with annotations in the source code pointing out the source of the problem.
• One-click login using GitHub account; all work is saved remotely to Firebase when logged in.
• Pop out preview of web page in its own window.
• Export to GitHub gist.
• Import starter code from a GitHub gist.

The validation system is the main point of this project. Most syntax checkers, linters, and style enforcers tend to provide feedback using language that is geared toward experienced coders, not beginners. Thus, providing a translation of error messages into plain English for students is the overriding concern of this project.

Popcode tends toward strict enforcement of lint and code style, even when enforced style decisions are arbitrary, under the philosophy that giving students one right way to do it eliminates ambiguity and aids the learning process.

Popcode uses React to render views, Redux to manage application state, Ace as the code editor, Webpack to package the client-side application, and Babel to compile modern JavaScript for compatibility with legacy browser versions.

Popcode detects mistakes in student code using slowparse, htmllint, HTML Inspector, Rework CSS, PrettyCSS, stylelint, jshint, and esprima.

Popcode is an all-volunteer project and contributions are welcome. I encourage first-time contributors to start with the Getting Started guide, which gives a friendly and detailed breakdown of each step toward contributing your first pull request.

If you want to get involved but don’t have a specific idea of how, check the good first issue and help wanted labels. If you already have an idea you’re passionate about, go for it.

Popcode comes with a batteries-included development environment built on nodeenv. You will need to have Python installed; any version 2.7+ will work. To set up the environment, run:

$ tools/setup.py

This will install node and yarn in an isolated environment in the nodeenv directory of the project root. It won’t interfere with any system-wide installation of those tools.

Once setup is complete, to run a development server, run:

$ tools/yarn.py start

This will start a server on http://localhost:3000

To start tests in watch mode, run:

$ tools/yarn.py autotest

Check the "scripts" section of package.json for other useful tools.

Popcode comes with a robust custom VS Code configuration, which is automatically enabled by tools/setup.py. If you use VS Code, you can:

• Run the Show Recommended Extensions command to easily install extensions that improve the Popcode developer experience
• Start a server, run tests, and more by typing task into the Quick Open bar to autocomplete the task to run
• Debug either your development environment or a Jest test by typing debug into the Quick Open bar

Popcode uses tools like Prettier, ESLint, and Stylelint to automatically format code. We recomment setting up editor plugins to auto-format on save; alternatively, you can run tools/yarn.py lintfix before committing to format and autofix lint. Popcode’s official VS Code integration (with recommended extensions installed) does this out of the box.

There is no requirement that you use the official development environment to work on Popcode; you’ll mostly just need the right versions of Node and Yarn installed on your machine (check the "engines" section of package.json for the current versions).

Popcode endeavors to use up-to-date technologies and code conventions to make development as pleasant as possible. Below are links to reference documentation on the major tools:

• React for constructing the user interface
• Redux for managing application state
• postcss-preset-env gives us cutting-edge CSS features
• Block Element Modifier provides a convention for organizing DOM classes
• Webpack builds the JavaScript
• Jest is the test framework

Popcode is distributed under the MIT license. See the attached LICENSE file for all the sordid details.

• Mat Brown (maintainer)
• Alejandro AR
• Vaibhav Verma
• Alex Pelan
• Carol Chau
• Jesse Wang
• Eric Lewis
• Razzi Abuissa
• Jeremy Schrader
• Leo McLay
• Frederic Brodbeck
• Ben Yelsey
• Aaron Greenberg
• Peter Jablonski
• Ten-Young Guh
• Ilona Brand
• Kaylee Knowles
• Felicia Wong
• Tim Miller
• Bruno Garcia
• Cory Etzkorn
• Nick Volpe
• Craig Iturbe
• Wylie Conlon
• Gary Pang
• Alessia Bellisario
• Roan Kattouw
• Harpreet Singh
• Limon Monte
• Matthew Armstrong
• Matt Garbis
• Ilya Gribov
• Chase Starr
• Alec Merdler
• Eric Snell
• Omar De Leo
• David Shen
• Maggie Walker
• Joshua Ling
• Taimur Samee
• Ronald Martin
• Ian Plunkett
• Adrian Falleiro
• Katie Conneally created the name Popcode
• Logo design, "Pop" concept, and branding elements by the team at Red Peak: Andrew Haug, Aya Kawabata, Jieun Lee, Achu Fones, Iwona Waluk, Stewart Devlin, and Katie Conneally
• User interface designed by Ariel Liu, Ian Jones, Meghan Knoll, and Simon Lesser.

These companies generously offer Popcode access to paid tiers of their excellent services, free of charge:

Feel free to email me at [email protected] if you have any questions.

You can find our Slack team, including our #dev channel, here.