TypeScript Beginner's Guide: Migrate from JavaScript the Right Way

TypeScript is JavaScript with a safety net. It doesn't replace JavaScript — it compiles down to it. But between writing your code and that compilation step, TypeScript checks your work: it catches the typo in that property name, the function call with the wrong argument type, the variable that might be undefined when you're treating it as a string. It finds bugs before they find you. This guide assumes you know JavaScript. We'll cover the key TypeScript concepts, then walk through a practical migration from an existing JS project — the right way, without breaking everything in one go. TL;DR TypeScript adds static types to JavaScript, catching bugs at compile time instead of runtime Install with npm install -D typescript and configure with tsconfig.json Core types: string , number , boolean , string[] , Record<K, V> , union types ( string | number ) interface and type are both valid — interface for object shapes, type for unions/primitives Migrate JS projects incrementally: start with a