Why I Switched from JavaScript to TypeScript (And Never Looked Back)

Two years ago, I was a die-hard JavaScript developer who thought TypeScript was unnecessary overhead. Today, I can't imagine building anything significant without it. Here's my story of transformation and why you might want to consider making the switch too.

The Trigger: A Production Bug

It started with a bug that cost us thousands of dollars and several sleepless nights. A simple typo in a property name went unnoticed through code reviews, tests, and QA. It shipped to production and caused a critical feature to silently fail.

// What we wrote
user.prefernces.theme = 'dark';

// What we meant
user.preferences.theme = 'dark';

That extra 'n' in "prefernces" was invisible to our eyes, our tests didn't catch it because we mocked the user object, and it worked just fine in our development environment—until it didn't in production.

The Resistance

Like many developers, I had my reasons for avoiding TypeScript:

1. "It's just JavaScript with extra steps" - Why add complexity?
2. "It slows down development" - All that typing takes time
3. "The learning curve is steep" - I have deadlines to meet
4. "Third-party libraries don't have types" - It'll be a mess

Spoiler alert: I was wrong about all of these.

The First Week: Pain

I won't lie—the first week was rough. Everything that used to take 5 minutes now took 15. Simple API calls required type definitions. My any types were everywhere, defeating the purpose.

// My first TypeScript code (embarrassing)
function fetchData(url: any): any {
  return fetch(url).then((res: any) => res.json());
}

I was ready to give up. But my team lead encouraged me to push through for just two weeks.

The Breakthrough

Something clicked in week two. I started thinking in types. Instead of rushing to code, I would:

1. Define my data structures first
2. Think about edge cases
3. Let the compiler guide me

Suddenly, TypeScript wasn't adding time—it was saving it.

The Benefits I Discovered

1. Catch Errors Before Runtime

That production bug that started this journey? Impossible with TypeScript:

interface User {
  id: string;
  preferences: {
    theme: 'light' | 'dark';
    notifications: boolean;
  };
}

// This would show an error immediately
user.prefernces.theme = 'dark';
//    ^^^^^^^^^^ Property 'prefernces' does not exist on type 'User'

2. Self-Documenting Code

Good code should be self-documenting. TypeScript makes this trivial:

interface ApiResponse<T> {
  data: T;
  status: number;
  message: string;
  timestamp: Date;
}

async function fetchUser(id: string): Promise<ApiResponse<User>> {
  // The return type tells me exactly what this function returns
  // No need to dig through implementation
}

3. Fearless Refactoring

Remember the fear of refactoring a large JavaScript codebase? Gone.

When I rename a property or change a function signature, TypeScript shows me every place that needs updating. No more "find all references" and hoping I caught everything.

4. Better IDE Support

The autocomplete in TypeScript is magical. My IDE knows:

• What properties an object has
• What parameters a function expects
• What methods are available
• What errors might occur

5. Team Communication

Types serve as a contract between team members:

// I write this
interface CreatePostData {
  title: string;
  content: string;
  tags: string[];
  published?: boolean;
}

// My teammate knows exactly what to pass
// No Slack messages needed!

The Challenges (And How I Overcame Them)

Challenge 1: Third-Party Libraries

Problem: Not all libraries have TypeScript definitions.

Solution: Most popular libraries do! For others:

• Check DefinitelyTyped (@types/library-name)
• Write simple definitions yourself
• Use declare module for quick fixes

Challenge 2: Complex Types

Problem: Generic types felt overwhelming.

Solution: Start simple, grow gradually:

// Week 1: Basic types
let name: string = 'John';

// Week 2: Interfaces
interface User {
  name: string;
  age: number;
}

// Week 4: Generics (not as scary as they look!)
function wrapInArray<T>(item: T): T[] {
  return [item];
}

Challenge 3: Build Configuration

Problem: Setting up TypeScript felt complicated.

Solution: Use templates:

• create-react-app --template typescript
• npx create-next-app@latest --typescript
• Most frameworks have TypeScript templates

Real-World Impact

After six months with TypeScript, our team saw:

• 60% fewer production bugs related to type errors
• 30% faster onboarding for new developers
• Reduced time debugging obvious issues
• Better code reviews focusing on logic, not syntax
• Increased confidence in refactoring

When TypeScript Might Not Be Right

To be fair, there are cases where TypeScript might be overkill:

• Quick prototypes or throwaway code
• Very small projects (< 100 lines)
• Learning basic JavaScript concepts
• Simple scripts or automation

But for any serious application? TypeScript pays dividends.

Tips for Making the Switch

1. Start Gradually

You don't need to convert everything at once. JavaScript and TypeScript can coexist:

// Your new files
import { oldFunction } from './old-javascript-file.js';

// Works perfectly fine!

2. Use strict: false Initially

Don't enable strict mode right away. Let your team get comfortable first.

{
  "compilerOptions": {
    "strict": false,
    // Enable these one at a time
    "noImplicitAny": false,
    "strictNullChecks": false
  }
}

3. Leverage Community Types

Install types for your dependencies:

npm install --save-dev @types/react @types/node

4. Use Type Inference

TypeScript is smart. You don't need to type everything:

// Unnecessary
const numbers: number[] = [1, 2, 3];

// TypeScript knows this is number[]
const numbers = [1, 2, 3];

5. Embrace unknown Over any

When you don't know a type, use unknown:

function handleApiResponse(data: unknown) {
  // Force yourself to validate
  if (typeof data === 'object' && data !== null) {
    // Now you can use it safely
  }
}

My Current TypeScript Setup

After two years, here's what I use:

{
  "compilerOptions": {
    "target": "ES2020",
    "lib": ["ES2020", "DOM"],
    "strict": true,
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "moduleResolution": "node",
    "resolveJsonModule": true,
    "noUnusedLocals": true,
    "noUnusedParameters": true,
    "noImplicitReturns": true
  }
}

The Verdict

Would I go back to JavaScript for a serious project? Absolutely not.

TypeScript has made me a better developer by:

• Forcing me to think about data structures
• Catching silly mistakes before they become bugs
• Making collaboration smoother
• Giving me confidence in my code

For the Skeptics

If you're still on the fence, I challenge you: Try TypeScript for just one project. Not a todo app—a real project with real complexity. Give it two weeks before judging.

I was skeptical too. Now I'm a convert. The initial time investment pays back exponentially.

Conclusion

Switching to TypeScript was one of the best decisions I made as a developer. It didn't make me write less code or work faster initially, but it made me write better code and catch issues earlier.

The question isn't whether to learn TypeScript—it's when. And in today's development landscape, the answer is probably "now."

Have you made the switch? What was your experience? I'd love to hear your thoughts!

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This is my personal experience. Your mileage may vary, but I encourage everyone to give TypeScript a fair shot.