What is TypeScript and should I learn it after JavaScript?

TypeScript is JavaScript with a type system layered on top. It's not a separate language you learn from scratch — it's JavaScript plus annotations that say what kind of value each thing holds, checked before your code runs. Any valid JavaScript is valid TypeScript. What it buys you, concretely. In JavaScript, `user.nmae` is a silent bug that returns `undefined` and blows up three functions later. In TypeScript, your editor underlines it immediately with 'Property nmae does not exist on type User'. Multiply that by every typo, every wrong argument order, every 'I thought this returned an array but it returns a promise', and you get why teams adopt it: a whole category of bugs stops reaching production, and the editor autocompletes accurately because it knows the shape of everything. The cost side, honestly: more code to write, occasional fights with the type checker over things you know are fine, and a genuinely confusing period around generics and complex types. On a small solo script it can feel like bureaucracy. On a codebase with several people and tens of thousands of lines, it pays for itself many times over — which is exactly why job listings ask for it. Should you learn it after JavaScript? Yes, and the order matters. Learn JavaScript properly first — types layered over a language you don't understand yet just adds confusion to confusion. Once you're comfortable writing JavaScript without constant reference to tutorials, TypeScript is a two-to-three week addition, not a restart. The practical on-ramp: 1. Learn basic annotations: `string`, `number`, `boolean`, arrays, and typing function parameters and return values. This is 80% of daily use and takes a couple of days. 2. Learn `interface` and `type` for describing object shapes — this is where the real value shows up, describing your API responses and data models. 3. Learn union types (`string | null`), optional properties, and how to handle values that might be missing. 4. Leave generics, utility types and conditional types until you hit a real need. They're the part that scares people and they're rarely needed early. A good way to start without a big commitment: convert one small existing project file by file. Rename `.js` to `.ts`, fix what the compiler complains about, and notice how many of the complaints are actual latent bugs. That experience converts more people than any argument.