What is TypeScript and why use it over JavaScript

TypeScript vs JavaScript

TypeScript is a statically typed superset of JavaScript. Every valid JavaScript file is also valid TypeScript. The key difference: TypeScript catches errors at compile time, before your code ever runs.

In JavaScript, this silently fails at runtime:

function add(a, b) {
  return a + b;
}
add("5", 10); // "510" — wrong, no warning

In TypeScript, the same mistake is caught immediately:

function add(a: number, b: number): number {
  return a + b;
}
add("5", 10); // Error: Argument of type 'string' is not assignable to parameter of type 'number'

What TypeScript adds

TypeScript gives you type annotations, interfaces, enums, generics, and access modifiers. These are stripped out during compilation — the output is plain JavaScript that runs anywhere.

The real value is developer experience: autocomplete knows what properties exist on an object, refactoring renames work across files, and bugs surface during development instead of in production.

When to use TypeScript

Use TypeScript on any project that will grow, be maintained by a team, or involve complex data structures. The upfront cost of adding types pays off quickly in reduced debugging time and safer refactors.