HTML Form Validation
Use required, min, max and pattern for immediate client-side feedback.
What this solves
Prevent an empty reorder-point input. This pattern is useful when the business question is clear but a generic tutorial is too abstract.
The rule
Combine native constraints with clear inline error messages.
<input type="number" min="0" required>Real-work checklist
- Define the business key and expected grain before writing the formula, query or markup.
- Test the pattern on a small known sample where you can verify the answer manually.
- Check missing values, duplicates and data types before trusting a large result.
- Scale to the real file or database only after the logic is proven.
Common mistake
Do not rely on browser validation alone for security on a server-backed app.