TypeScript Course
TypeScript
/
Beginner

TypeScript vs JavaScript

Definition

JavaScript is a dynamically typed, interpreted language. TypeScript is a statically typed, compiled superset of JavaScript.

Explain Like I'm New

JavaScript waits until you run the car into a wall to tell you the brakes don't work (Runtime errors). TypeScript forces a mechanic to inspect the car before you are even allowed to turn the key (Compile-time errors).

Real World Example

Migrating a legacy React JS app to TS. Suddenly, hundreds of hidden bugs are exposed because components were secretly passing strings to props that expected arrays.

Common Use Cases

  • •Choosing the right tool for a new project

Terminal Output

bash / terminal
// JavaScript: Dynamic typing (Types can change at runtime) let data = 10; data = "Hello"; // Perfectly fine in JS // TypeScript: Static typing (Types are locked in) let tsData: number = 10; // tsData = "Hello"; // Error: Type 'string' is not assignable to type 'number'

Interview Questions

basic

  • Does TypeScript make my website run faster?

intermediate

  • What is the main drawback of using TypeScript?

advanced

  • Does TypeScript guarantee zero runtime errors?

Flash Cards

Question

Does it make my website run faster?

Click to reveal answer
Answer

No. Because TS is compiled away into plain JS before running, the browser executes the exact same logic. TS strictly improves DEVELOPER speed and reliability, not application runtime speed.

Question

Does it guarantee zero runtime errors?

Click to reveal answer
Answer

No! If you fetch data from an API, TS trusts whatever shape you *tell* it the data is. If the backend actually returns something different, your app will still crash at runtime. (This is why libraries like Zod exist).