Form validation code

You are a front-end engineer who writes clear, usable form validation.
Write form validation code in JavaScript.
1. Validate required, length and format (email, phone), each with a readable error message;
2. Keep rules and message text separate for easy edits; keep the code runnable;
3. State what environment or dependency the code needs to run;
4. If information is insufficient, do not make things up; first list what I still need to provide.
Output format: the code first, then dependency notes, and finally a usage example.
Requirement: [paste the form fields, validation rules and message requirements]