TypeScript مقابل JavaScript 2026: هل يجب عليك استخدام TypeScript؟

// JavaScript (valid TypeScript too)
function greet(name) {
  return "Hello, " + name;
}

// TypeScript (added type annotations)
function greet(name: string): string {
  return "Hello, " + name;
}

// TypeScript removes types at compile time
// Output JavaScript is identical: function greet(name) { return "Hello, " + name; }

// 1. Type safety — catch bugs before runtime
function divide(a: number, b: number): number {
  return a / b;
}
divide(10, "2");  // TypeScript ERROR: Argument of type 'string' is not assignable to parameter of type 'number'
// In JavaScript: silently returns NaN!

// 2. Autocomplete — better IDE support
interface User { id: number; name: string; email: string; }
const user: User = { id: 1, name: "Alice", email: "alice@example.com" };
user.  // IDE shows: id, name, email — no guessing!

// 3. Interfaces and types — document your data shapes
type Status = "pending" | "active" | "inactive";
interface ApiResponse<T> { data: T; error: string | null; }

// 4. Generics — reusable type-safe code
function first<T>(arr: T[]): T | undefined {
  return arr[0];
}
const num = first([1, 2, 3]);   // type: number | undefined
const str = first(["a", "b"]); // type: string | undefined

# Add TypeScript to existing JS project
npm install --save-dev typescript @types/node

# Generate tsconfig.json
npx tsc --init

# Start with allowJs: true — migrate gradually
# tsconfig.json:
# {
#   "compilerOptions": {
#     "allowJs": true,      # allow .js files
#     "checkJs": false,     # don't type-check JS yet
#     "strict": false,      # start permissive
#     "outDir": "dist"
#   }
# }

# Rename files: .js → .ts one at a time
# Fix type errors gradually
# Enable strict mode after most files migrated