Understanding the TypeScript Mental Model Many developers struggle with TypeScript not because it is hard — but because they misunderstand what it actually is. Let’s fix that first. TypeScript Is Not a Runtime Language TypeScript does not run in production. It compiles into JavaScript. TypeScript → Compiler → JavaScript → Runtime Enter fullscreen mode Exit fullscreen mode Types exist only during development. The Core Idea TypeScript adds static analysis to JavaScript. Its job is to answer: “Can this code break before we run it?” 1. Type Annotations let age: number = 30; You describe expected values. 2. Function Types function add(a: number, b: number): number { return a + b; } Think of this as a contract. 3. Interfaces (The Most Important Concept) interface User { id: number; name: string; } Interfaces describe data shape — not behavior. Most real TypeScript usage revolves around this idea. 4. Type Inference You usually don’t write types manually. const name = "Ali"; TypeScript already knows it’s a string.…