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

function add(a, b) {
  return a + b;
}

add(10, "5"); // "105" unexpected

Same idea in TypeScript

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

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