Lesson 04 · The DOM
Forms & Validation in the Browser
Read form values at the right moment, handle submit without a page reload, validate with the constraint validation API, give feedback people can perceive, and collect everything with FormData.
Prerequisites: Events: Responding to Your User
Learning objectives
By the end of this lesson, you will be able to:
- Read text, checkbox and select values, and choose between input and change by intent
- Handle the submit event with preventDefault instead of a page reload
- Validate with constraints, checkValidity, validationMessage and setCustomValidity
- Give inline feedback with aria-invalid, error regions and focused first errors
- Collect every field at once with the FormData API