TypeScript Strict Mode Fixer

I'm enabling strict mode in TypeScript and need help fixing the errors.

**tsconfig.json settings:**
```json
{
  "compilerOptions": {
    "strict": true,
    [other relevant settings]
  }
}
```

**Error-prone code:**
```typescript
[paste code with type errors]
```

**Error messages:**
```
[paste TypeScript error messages]
```

**Context:**
- Framework: [React/Vue/Angular/Node]
- External libraries causing issues: [list them]
- Preferred typing approach: [strict/pragmatic]

Please help me:
1. Fix each error with proper typing
2. Explain why each error occurs
3. Provide type-safe alternatives
4. Create necessary type definitions
5. Suggest best practices for avoiding similar issues