TypeScript vs JavaScript

Go with TS if:

• high fluctuation
• using cypress to do UI-Tests
• doing agile software development:
  • pair programming
  • TDD
  • agile methodologies according to agile manifest: DoD, DoR, etc.
• following clean code principles
• doing Angular (opinionated framework)
• doing React / Vue
• caring about code quality
• writing tests in Jest/Jasmine
• utilizing IDE features to autocomplete, refactor, especially in IntelliJ

Go with JS if

• creating a POC app in 1 hour
• creating a mock server for local development
• creating a quick script in Fastify to host a SPA application