TypeScript Intro

TypeScript is a programming language built on top of JavaScript. Simple idea: TypeScript = JavaScript + types. That means: - everything you can do in JavaScript, you can do in TypeScript - plus you get extra rules that catch mistakes early ## Why TypeScript was created JavaScript is very flexible. But flexibility also means: - bugs show up at runtime - large code becomes hard to understand - refactoring is risky TypeScript adds a type system so many errors are caught: - while writing code - before running the app ## JavaScript vs TypeScript (simple view) JavaScript: - dynamic - fast to start - errors appear when code runs TypeScript: - typed - safer - errors appear while coding ## Example: problem in JavaScript ```js function add(a, b) { return a + b; } add(10, "5"); // "105" unexpected ``` ## Same idea in TypeScript ```ts function add(a: number, b: number): number { return a + b; } add(10, 5); // OK add(10, "5"); // Error before running ``` TypeScript warns you before the app even runs. ## Why TypeScript matters today (AI era too) Modern apps: - huge frontends (React, Angular, Vue) - APIs, cloud systems - AI pipelines and dashboards In such systems: - many developers work together - code lives for years - mistakes are expensive TypeScript helps by: - documenting intent through types - making code self-explanatory - enabling better AI code tools because structure is clear ## How TypeScript works You write .ts files. TypeScript compiler converts them into .js files. Browsers and Node.js run JavaScript, not TypeScript. ## Graph: TypeScript flow ```mermaid flowchart LR A[TypeScript code .ts] --> B[TypeScript Compiler] B --> C[JavaScript .js] C --> D[Browser / Node.js] ``` ## Remember - TypeScript is JavaScript with safety - it catches errors early - it scales better for large projects