Hey there! You're probably reading this because you've been invited to take one of our code challenges or are working on an Outlier engineering project. Welcome!

We're looking for talented developers to help us shape the future of education. Our platform has the world's best online, university-level courses, taught by some of the most celebrated educators in the world. Our courses use the active learning method to help students visualize, understand, and enjoy learning.

Code quality is very important to us, and we hope it is to you too. In this guide we'll share our engineering process that we use to ensure that we can build quickly while keeping our projects stable and maintainable. We'll cover topics like code style, commit guidelines, project workflow, and team communication.

Some developers feel the need to debate code style. Other engineers will use the project's style and get stuff done. We prefer engineers who get stuff done. Consistency is important, please follow these guidelines.

We use the JavaScript Standard Style in our code. This is the style used by npm, GitHub, Zeit, MongoDB, Express, Electron, and many others. Be sure to use an automatic formatter like standard-formatter for Atom and vscode-standardjs for Visual Studio Code.

Line length should be limited to 80 characters.

• Code should be as simple, explicit, and as easy to understand as possible.
• Functional style is preferred to OOP. When possible functions should be pure and not rely on shared state or side effects.
• Avoid large frameworks; use small modules that are easy to understand.
• Modules must use this order so that they can be understood quickly when skimmed:
  1. External dependencies: anything listed in package.json, e.g. require('http')
  2. Internal dependencies: any files created in the project itself, e.g. require('./api')
  3. Constants and other setup: this includes anything absolutely necessary to be defined before module.exports
  4. Exports: module.exports should be as close to the beginning of the file as possible. The module should export either a single function or a "catalog object", e.g. module.exports = { method1, method2, ... }
  5. Functions: these go after the above sections. Use function hoisting to control the placement of your functions so that important, high-level functions are above smaller more-general utility functions.
• Use descriptive variable names. Function names should be a verb like route() or verb combined with a noun like routeRequest().
• Keep your functions short. If your function is over 40 lines, you should have a good reason.
• Functions should not accept more than 3 arguments. Use a single options object if you need more arguments.
• Keep nesting to a minimum. Use early returns, single-line conditionals, and function calls.

Version control is a project's best source of documentation when done correctly. When trying to understand code it's extremely useful to use git blame to find both the PR and the issue associated with that change.

PRs should be small and focused. Each commit should solve a single problem and be covered by a test that exemplifies that particular feature or fix.

All PRs must be reviewed by a teammate before they are eligle to be merged into the master branch. Large PRs are difficult to review. Be sure to break large PRs into smaller ones so that they can be reviewed quickly and deployed to production.

• Never commit passwords, access tokens, or other credentials into version control. If you think you absolutely have to, ask first. If you do this by accident, tell someone immediately.
• Each commit should be as small and as simple as possible.
• The project must be operational and have all tests passing after every commit.
• Use Conventional Commits
  • See the "Commit Types" section below
  • Valid types are chore:, docs:, style:, refactor:, perf:, and test:
• Do not mix feature changes (added functionality) with fixes (restored functionality), refactors (no change in functionality), or style changes (only whitespace or other cosmetic changes).
• Before a PR is ready for review, make sure that it is a single commit. If the combined commit is too large or disparate, consider multiple PRs.
• Do not modify a project's .gitignore to add files related to your editor or environment. Use your own global .gitignore for that instead.

We use Zenhub to manage our workflow. Each task is represented by an issue. Be sure to connect any PR you are working on to the appropriate issue. Do this via the Zenhub interface and by adding Closes #X where X is the issue number to the PR description in Github.

As tasks move from Backlog to In Progress to Needs Review to Needs QA to Ready to Deploy and finally to Closed.

• Backlog: This is where you will choose from issues to work on. Once you have selected one, move it to In Progress.
• In Progress: While you are working on an issue, it should stay in this column. Once you are finished and satisfied with your work, move it to Needs Review.
• Needs Review: Each day you should be looking at this column for PRs to review. This column will list all issues that are complete and are waiting on review before they can be ready for deploy. When you review an item, make sure that it follows all of our coding principles and will not cause problems when we deploy it to production. Once a PR has been reviewed, either move it back to In Progress or forward to Needs QA or Ready to Deploy. Do not allow items to sit in Needs Review.
• Needs QA: If the change affects the front-end and can be tested with a deploy preview it should be tested by QA. After successful testing it should be moved to Ready to Deploy, but if it is unsatisfactory, it should be moved back to In Progress.
• Ready To Deploy: After an issue is finished and has been reviewed and approved by a teammate, it will be moved to this column. After it has been deployed, it will be moved to the Closed column.

Commit types (e.g. feat, fix, refactor, style) are important because they are a signal to the reviewer for what they should be looking for and how much scrutiny the review needs.

Feature commits require the most scrutiny. They add or change functionality, require additional tests, and have the greatest chance of introducing a bug.

Fix commits are smaller and have a more bounded scope than feature commits. Features usually introduce multiple new behaviors, but fix commits will only modify a single behavior. Fix commits need to provide additional test coverage because the existing tests were insufficient to catch the error. Feature commits should have multiple tests for these behaviors, but fix commits typically introduce a single test to prove that the error has been fixed (test should fail without the fix inactive and pass with it active). These commits can introduce additional bugs, but it’s less common than feature commits.

Refactors need less scrutiny than feature or fix commits because little about the app changes. All consumers of the refactored part of the app should be 100% unaware of the change. If module A is refactored, and module B depends on A, module B does not need to be tested because A hasn’t changed anything from their perspective. Similarly, anything that depends on B doesn’t need to be tested either, no change should bubble up to cause issues. Since nothing is changing, any existing tests/QA should already be sufficient to catch any issues created by the refactor. Refactors don’t generate additional tests.

Style commits need the least amount of scrutiny. They tend to be very repetive (converting from snake_case to camelCase, standardizing indentation, or changing newlines). These changes will have no functional impact on the code and any existing tests should be sufficient.

Reference from Angular:

• build: Changes that affect the build system or external dependencies (example scopes: gulp, broccoli, npm)
• ci: Changes to our CI configuration files and scripts (example scopes: Travis, Circle, BrowserStack, SauceLabs)
• docs: Documentation only changes
• feat: A new feature
• fix: A bug fix
• perf: A code change that improves performance
• refactor: A code change that neither fixes a bug nor adds a feature
• style: Changes that do not affect the meaning of the code (white-space, formatting, missing semi-colons, etc)
• test: Adding missing tests or correcting existing tests