TypeScript

This is for people who already write basic JavaScript and want the compiler to catch wrong data before the code runs. You will add types to JavaScript you already know, compile with tsc, and stop guessing what a function accepts. If you skip the basics and add any until the red lines go away, you keep the old bugs and add a build step.

This is for people who can write basic TypeScript and now work on code that other people also touch. You will use generics, utility types and third-party typings so shared code stays honest when the data changes. If you keep reaching for any and as at every boundary, the compiler stops helping exactly where the bugs are.

You'll design declaration files, deep conditional types and migration paths so a real codebase stays typed as it grows.