Jeff Bruchado
Back to blog

TypeScript in 2025: Why 38.5% of Developers Chose It and You Should Too

Hey HaWkers, TypeScript is at 38.5% popularity according to 2025 surveys, consolidating as one of the top 5 programming languages in the world. But is it just hype or are there solid reasons to adopt?

In this article, we'll explore why TypeScript dominated the JavaScript ecosystem, how to start practically and migration strategies for existing projects.

Why TypeScript Won the Battle

1. Type Safety Prevents Expensive Bugs

// ❌ JavaScript: Bug only appears in production
function calculateDiscount(price, percentage) {
  return price - (price * percentage / 100);
}

// Bug: someone passes string by mistake
calculateDiscount('100', 20); // '100-NaN' = NaN 😱

// ✅ TypeScript: Error detected at development time
function calculateDiscount(price: number, percentage: number): number {
  return price - (price * percentage / 100);
}

// Compile-time error!
calculateDiscount('100', 20);
// Error: Argument of type 'string' is not assignable to parameter of type 'number'

2. Powerful IntelliSense and Autocomplete

// TypeScript provides precise autocomplete
interface User {
  id: string;
  name: string;
  email: string;
  role: 'admin' | 'user' | 'guest';
  createdAt: Date;
  metadata?: {
    lastLogin?: Date;
    preferences: {
      theme: 'light' | 'dark';
      notifications: boolean;
    };
  };
}

function greetUser(user: User) {
  // IDE suggests all available properties
  console.log(`Hello, ${user.name}!`);

  // Autocomplete on nested objects
  if (user.metadata?.preferences.theme === 'dark') {
    // IDE knows exactly what's available
    console.log('Dark mode enabled');
  }

  // Literal types prevent typos
  if (user.role === 'admim') { // Error: 'admim' doesn't exist
    // ...
  }
}

3. Safe Refactoring in Large Codebases

// Scenario: Rename property in 100 files

// Original interface
interface Product {
  productName: string;
  price: number;
}

// Refactor to 'name' instead of 'productName'
interface Product {
  name: string; // TypeScript shows ALL places that broke
  price: number;
}

// All uses are automatically identified
function displayProduct(product: Product) {
  return `${product.productName} - $${product.price}`;
  // Error: Property 'productName' does not exist on type 'Product'
  // Suggestion: Did you mean 'name'?
}

// In JavaScript: You'd discover this bug in production 💥

TypeScript in Practice: From Basic to Advanced

Primitive and Basic Types

// Basic types
let isDone: boolean = false;
let count: number = 42;
let name: string = 'John';
let notSure: any = 4; // Avoid using 'any'!

// Arrays
let numbers: number[] = [1, 2, 3];
let strings: Array<string> = ['a', 'b', 'c'];

// Tuples (arrays with fixed types)
let tuple: [string, number] = ['age', 30];

// Enum
enum Status {
  Pending = 'PENDING',
  Approved = 'APPROVED',
  Rejected = 'REJECTED'
}

const orderStatus: Status = Status.Pending;

// Union Types (alternative types)
let id: string | number;
id = '123'; // OK
id = 123;   // OK
id = true;  // Error

// Literal Types (specific values)
type HttpMethod = 'GET' | 'POST' | 'PUT' | 'DELETE';

function makeRequest(url: string, method: HttpMethod) {
  // method can only be one of the specified values
}

makeRequest('/api/users', 'GET');     // OK
makeRequest('/api/users', 'PATCH');   // Error

Interfaces and Type Aliases

// Interface: Define object structure
interface User {
  id: string;
  name: string;
  email: string;
  age?: number; // Optional
  readonly createdAt: Date; // Readonly
}

// Extending interfaces
interface AdminUser extends User {
  permissions: string[];
  role: 'admin';
}

// Type Alias: Similar to interface, but more flexible
type Point = {
  x: number;
  y: number;
};

// Type for union types
type ID = string | number;

// Type for functions
type GreetFunction = (name: string) => string;

const greet: GreetFunction = (name) => `Hello, ${name}!`;

Generics: Reusable Types

// Simple generic
function identity<T>(arg: T): T {
  return arg;
}

const num = identity<number>(42);
const str = identity<string>('hello');

// Generic with constraints
interface HasLength {
  length: number;
}

function logLength<T extends HasLength>(arg: T): T {
  console.log(arg.length); // OK, T has length
  return arg;
}

logLength('hello');     // OK, string has length
logLength([1, 2, 3]);   // OK, array has length
logLength(42);          // Error, number doesn't have length

// Generic in interfaces
interface Response<T> {
  data: T;
  status: number;
  message: string;
}

interface User {
  id: string;
  name: string;
}

const userResponse: Response<User> = {
  data: { id: '1', name: 'John' },
  status: 200,
  message: 'Success'
};

Gradual Migration from JavaScript to TypeScript

Migration Strategy

// 1. Initial configuration (tsconfig.json)
{
  "compilerOptions": {
    "target": "ES2020",
    "module": "ESNext",
    "lib": ["ES2020", "DOM"],
    "jsx": "react-jsx",
    "strict": false, // Start with false, enable gradually
    "allowJs": true, // Allow .js files during migration
    "checkJs": false, // Don't check .js files initially
    "esModuleInterop": true,
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true,
    "resolveJsonModule": true,
    "isolatedModules": true,
    "noEmit": true
  },
  "include": ["src"],
  "exclude": ["node_modules"]
}

// 2. Migration plan
const migrationPlan = {
  'Phase 1 - Setup': [
    'Install TypeScript and types',
    'Configure tsconfig.json',
    'Rename 1 file .js → .ts to test',
    'Configure build pipeline'
  ],
  'Phase 2 - New Files': [
    'All new files in TypeScript',
    'Create types.d.ts for common interfaces'
  ],
  'Phase 3 - Gradual Migration': [
    'Migrate utility modules first',
    'Migrate independent components',
    'Migrate components with dependencies',
    'Enable strict mode gradually'
  ],
  'Phase 4 - Strictness': [
    'Enable noImplicitAny',
    'Enable strictNullChecks',
    'Enable strictFunctionTypes',
    'Enable strictPropertyInitialization'
  ]
};

TypeScript with Popular Frameworks

React + TypeScript

import React, { useState, useEffect } from 'react';

// Typed props
interface UserCardProps {
  user: {
    id: string;
    name: string;
    email: string;
    avatar?: string;
  };
  onEdit?: (userId: string) => void;
  onDelete?: (userId: string) => void;
}

// Typed functional component
export function UserCard({ user, onEdit, onDelete }: UserCardProps) {
  const [isHovered, setIsHovered] = useState<boolean>(false);

  useEffect(() => {
    console.log('User card mounted:', user.id);

    return () => {
      console.log('User card unmounted:', user.id);
    };
  }, [user.id]);

  const handleEdit = () => {
    onEdit?.(user.id); // Safe navigation operator
  };

  return (
    <div
      onMouseEnter={() => setIsHovered(true)}
      onMouseLeave={() => setIsHovered(false)}
      className={isHovered ? 'card-hovered' : 'card'}
    >
      {user.avatar && <img src={user.avatar} alt={user.name} />}
      <h3>{user.name}</h3>
      <p>{user.email}</p>

      <button onClick={handleEdit}>Edit</button>
      {onDelete && (
        <button onClick={() => onDelete(user.id)}>Delete</button>
      )}
    </div>
  );
}

Next.js + TypeScript

// app/page.tsx (App Router)
import { Metadata } from 'next';

export const metadata: Metadata = {
  title: 'Home Page',
  description: 'Welcome to my site'
};

interface HomePageProps {
  searchParams: { [key: string]: string | string[] | undefined };
}

export default async function HomePage({ searchParams }: HomePageProps) {
  // Typed server component
  const data = await fetchData();

  return (
    <div>
      <h1>Welcome</h1>
      <DataDisplay data={data} />
    </div>
  );
}

// Typed API Route
// app/api/users/route.ts
import { NextRequest, NextResponse } from 'next/server';

interface UserPayload {
  name: string;
  email: string;
}

export async function POST(request: NextRequest) {
  try {
    const body: UserPayload = await request.json();

    // Validation
    if (!body.name || !body.email) {
      return NextResponse.json(
        { error: 'Missing required fields' },
        { status: 400 }
      );
    }

    // Create user
    const user = await createUser(body);

    return NextResponse.json(user, { status: 201 });
  } catch (error) {
    return NextResponse.json(
      { error: 'Internal server error' },
      { status: 500 }
    );
  }
}

Conclusion: Is TypeScript Worth It?

Yes, absolutely. TypeScript is no longer a trend — it's the new standard for professional JavaScript in 2025.

Concrete benefits:

  • Fewer bugs: Errors detected before production
  • Better DX: Autocomplete and safe refactoring
  • More maintainable code: Living documentation via types
  • Career: 68% of jobs require TypeScript

If you want to master JavaScript and TypeScript in a structured way, I recommend checking out another article: Functional Programming in JavaScript: Understanding Higher-Order Functions where you'll discover patterns that work perfectly with TypeScript.

Let's go! 🦅

📚 Want to Deepen Your JavaScript Knowledge?

This article covered TypeScript, but mastering solid JavaScript is the foundation for everything.

Developers who invest in structured knowledge tend to have more opportunities in the market.

Complete Study Material

If you want to master JavaScript from basics to advanced, I've prepared a complete guide:

Investment options:

  • $4.90 (single payment)

👉 Learn About JavaScript Guide

💡 Material updated with industry best practices

Comments (0)

This article has no comments yet 😢. Be the first! 🚀🦅

Add comments