Code walkthrough: practical slice

Hands-on walkthrough

Below is a minimal pattern you can adapt while following Choosing and Customizing WordPress Themes for E-Commerce. Names are illustrative; match your stack and framework.

Example: structure

// 1) Parse & validate input
function handleRequest(input) {
  const parsed = validate(input);
  if (!parsed.ok) return errorResponse(parsed.errors);
  // 2) Run domain logic (pure)
  const result = compute(parsed.value);
  // 3) Map to response DTO
  return okResponse(toDto(result));
}

Why this shape

1. Validation fails fast and returns structured errors.
2. Core logic stays isolated from HTTP or UI details.
3. Responses are stable contracts for tests and clients.

Extend with logging, metrics, and retries at the boundaries—not inside pure functions.