How to fix A required parameter cannot follow an optional parameter in TypeScript

// ERROR: Optional before required
function processData(filter?: string, data: DataObject) {
  // ...
}

// FIXED: Required before optional
function processData(data: DataObject, filter?: string) {
  // ...
}

// ERROR in arrow function
const handler = (id?: number, name: string) => {
  // ...
};

// FIXED
const handler = (name: string, id?: number) => {
  // ...
};

// ERROR in class method
class UserService {
  getUser(id?: string, includeProfile: boolean) {
    // ...
  }
}

// FIXED
class UserService {
  getUser(includeProfile: boolean, id?: string) {
    // ...
  }
}

// ERROR: Optional before required
function calculate(a?: number, b: number, c: number) {
  // ...
}

// FIXED: Use default value instead of optional
function calculate(a: number = 0, b: number, c: number) {
  // ...
}

// Even better: Put required parameters first
function calculate(b: number, c: number, a: number = 0) {
  // ...
}

// With multiple optional parameters
function createUser(
  username: string,
  email: string = "",
  isAdmin: boolean = false,
  createdAt: Date = new Date()
) {
  // All required parameters come first
  // Optional parameters with defaults come last
}

// ERROR: Complex mixed parameters
function search(
  query: string,
  limit?: number,
  offset: number,
  sortBy?: string,
  ascending: boolean
) {
  // ...
}

// FIXED: Use options object
interface SearchOptions {
  query: string;           // Required
  limit?: number;          // Optional
  offset: number;          // Required
  sortBy?: string;         // Optional
  ascending: boolean;      // Required
}

function search(options: SearchOptions) {
  const { query, limit = 10, offset, sortBy = "date", ascending } = options;
  // ...
}

// Cleaner usage
search({
  query: "typescript",
  offset: 0,
  ascending: true,
  // limit and sortBy are optional
});

// With destructuring in function signature
function search({
  query,
  limit = 10,
  offset,
  sortBy = "date",
  ascending
}: SearchOptions) {
  // ...
}

// ERROR in interface
interface DataProcessor {
  process(data: any, filter?: string, validate: boolean); // filter? before validate
}

// FIXED
interface DataProcessor {
  process(data: any, validate: boolean, filter?: string);
}

// ERROR in type alias
type Handler = (id?: string, payload: any) => void;

// FIXED
type Handler = (payload: any, id?: string) => void;

// ERROR in generic function type
type Transformer<T> = (input?: T, options: TransformOptions) => T;

// FIXED
type Transformer<T> = (options: TransformOptions, input?: T) => T;

// Function with overloads
function configure(config: string): void;
function configure(config: string, options: ConfigOptions): void;
function configure(config: string, options?: ConfigOptions): void {
  // Implementation handles both cases
  if (options) {
    // With options
  } else {
    // Without options
  }
}

// Usage
configure("production");
configure("development", { debug: true });

// Another example with different types
function parse(input: string): ParsedResult;
function parse(input: string, strict: boolean): ParsedResult;
function parse(input: string, strict?: boolean): ParsedResult {
  // Implementation
  return { /* ... */ };
}

// Original (error)
function process(userId?: string, data: UserData) {
  // ...
}

// Calls that need updating
process("user123", userData);      // userId = "user123", data = userData
process(undefined, userData);      // userId = undefined, data = userData

// Fixed function
function process(data: UserData, userId?: string) {
  // ...
}

// Updated calls (swap arguments)
process(userData, "user123");      // data = userData, userId = "user123"
process(userData);                 // data = userData, userId = undefined

// Use a linter to find all call sites
// In VS Code: Search for function name
// Or use: grep -r "process(" src/