recommendations.md

Recommendation for Production

Development Policy

• The developer ("the dev" in short) must use TypeScript with no escape hatches. The use of any keyword and all type-assertions without runtime validations such as with as keyword and use of ! are strictly forbidden. Asserting with unknown keyword instead of any is allowed.
• The dev has to format the code using the Prettier configuration in the workspace.
• The dev needs to lint the code using ESLint & TSLint rules configured in the same workspace.
• The dev should use the most common and industry-standard naming conventions of TypeScript/ECMAScript community.
• The developer should use only a single source of truth for the local storage unless it causes a significant performance issues.

Defensive Programming Tips

• Use static types.
• Avoid directly setting null or undefined. Instead, wrap them in an Option or Maybe type.
• Handle errors using a Result or Either type.
• Prefer exhaustive pattern matching over conditional statements.
• Prefer early returns.
• Isolate side effects from pure functions with a clear separation between the two.
• Mutation is fine only if your function/component is idempotent.
• Declare variables as close to their usage as possible. Avoid setting global variables.
• Your code must explicitly show at compile time what can fail or throw exceptions. You can use type-level abstraction for this.
• Make your code auto-testable or provable. Don't depend on manual tests.
• Write tests. Not too many. Mostly integration tests.
• Prefer generating tests over writing tests whenever possible.
• Use state machines.
• Use defensive copying for time-travel debugging. Avoid copying if it causes unnecessary overhead.