What Is TypeScript and Why Should You Use It?

What Is TypeScript?

TypeScript is a programming language developed by Microsoft that builds on JavaScript by adding static type definitions. TypeScript code is transpiled to plain JavaScript before running in a browser or Node.js environment.

TypeScript is an open-source superset of JavaScript. Any valid JavaScript code is also valid TypeScript. Developers can adopt TypeScript gradually, adding types to existing JavaScript codebases incrementally.

Why Types Matter

JavaScript is dynamically typed. Variables can hold any value, and type errors are not caught until the code runs. Consider this example:

javascript
function getUser(id) {
  return fetchUser(id);
}

const user = getUser("not-a-number");
console.log(user.name.toUpperCase()); // Crashes if user is null

With TypeScript:

typescript
async function getUser(id: number): Promise<User | null> {
  return fetchUser(id);
}

const user = await getUser(42);
if (user) {
  console.log(user.name.toUpperCase()); // TypeScript knows user is not null here
}

The TypeScript compiler and editor tooling catch the potential null reference before the code runs.

Core TypeScript Features

Interfaces and Types

Define the shape of objects:

typescript
interface User {
  id: string;
  email: string;
  name: string;
  role: "admin" | "member";
}

Generics

Write code that works across multiple types while remaining type-safe:

typescript
function first<T>(arr: T[]): T | undefined {
  return arr[0];
}

Type Inference

TypeScript infers types from context. Explicit annotations are often unnecessary:

typescript
const numbers = [1, 2, 3]; // TypeScript infers number[]
const doubled = numbers.map(n => n * 2); // TypeScript infers number[]

Benefits for Development Teams

Catch Errors Early

TypeScript finds type errors at compile time, before code is deployed.

Better IDE Support

Because types describe the shape of every value, editors can provide reliable autocomplete, hover documentation, and refactoring tools.

Safer Refactoring

When you rename a property or change a function signature, the TypeScript compiler identifies every place that must be updated.

TypeScript in the Ecosystem

TypeScript is supported natively by all major frameworks:

Next.js creates TypeScript projects by default
React, Vue, Angular, and Svelte all have first-class TypeScript support
ORMs including Prisma and Drizzle generate TypeScript types from database schemas

Conclusion

TypeScript improves code quality, catches errors earlier in the development cycle, and enables better tooling. For web application projects of any significant size, TypeScript is the standard choice among professional development teams.

What Is TypeScript and Why Should You Use It?