- Development mode includes warnings that help detect bugs but increases bundle size and slows performance.
- The __DEV__ constant is replaced at build time, and minifiers remove dead code in production.
- The process.env.NODE_ENV pattern is substituted with a string literal by bundlers like webpack.
- Dead code elimination requires static conditions; complex expressions or module boundaries may not work.
- Modern tools like Create React App separate development and production builds into distinct commands.
- Development warnings should be on by default to catch bugs early, especially for new users.
- The convention of process.env.NODE_ENV originated from Node.js and was adopted by browserify and React.
- React now precompiles separate bundles for development and production to avoid runtime checks.
- The article advocates for modes as a first-class concept in JavaScript environments.