Addresses issue #7932: Add comprehensive documentation on input validation for JavaScript, including best practices for validating empty parameters and using guard clauses to prevent runtime errors.

This entry provides developers with:

• Clear explanation of input validation concepts
• Common validation techniques (empty/null checks, type checks, length checks, format checks, range checks)
• Practical example showing guard clause implementation for empty parameter validation
• Best practices for implementing robust input validation
• Cross-references to related concepts

Description

Issue Solved

Type of Change

• Adding a new entry
• Editing an existing entry (fixing a typo, bug, issues, etc)
• Updating the documentation

Checklist

• All writings are my own.
• My entry follows the Codecademy Docs style guide.
• My changes generate no new warnings.
• I have performed a self-review of my own writing and code.
• I have checked my entry and corrected any misspellings.
• I have made corresponding changes to the documentation if needed.
• I have confirmed my changes are not being pushed from my forked main branch.
• I have confirmed that I'm pushing from a new branch named after the changes I'm making.
• I have linked any issues that are relevant to this PR in the Issues Solved section.