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React Academy · Lesson

Basic Validation Patterns & Submit Handling

Apply simple form checks (required fields, length, basic email) and handle submit by preventing reload and reporting errors.

Basic Validation Patterns & Submit Handling is a free React Academy lesson on CoddyKit — lesson 2 of 3. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the React Academy learning path, one of 3 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why validate?

Goal: Add simple checks to forms and handle submit smoothly.

  • Required fields
  • Length checks
  • Basic email pattern

Submit flow

A typical flow:

  • onSubmit calls event.preventDefault()
  • Run validations
  • If no errors: proceed (send or show success)
  • If errors: set state and display messages

Rules to start with

Start small:

  • Required: value.trim().length > 0
  • Length: at least N characters
  • Email: basic check like value.includes("@") for beginners

Demo: validate & submit

Handle submit with preventDefault(), validate, and show inline errors stored in state.


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Better error UX

Error UX tips:

  • Show messages near fields
  • Keep text short and helpful
  • Disable submit only when necessary

Pitfalls

Avoid:

  • Forgetting preventDefault() on submit
  • Using uncontrolled inputs with validation state
  • Huge regexes early—start simple and improve later

Submit handling check

What should a React form submit handler do first to avoid page reload?

Recap

Recap: Prevent reload with event.preventDefault(), run simple checks (required/length/email), and display errors from state next to fields.

Frequently asked questions

Is the “Basic Validation Patterns & Submit Handling” lesson free?

Yes — the full text of “Basic Validation Patterns & Submit Handling” is free to read here on the web, and the React Academy course includes 3 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the React Academy course, upgrade to CoddyKit PRO.

What will I learn in “Basic Validation Patterns & Submit Handling”?

Apply simple form checks (required fields, length, basic email) and handle submit by preventing reload and reporting errors. You practise React Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start React Academy?

No prior experience is required. React Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 3, so you can start here or from the beginning and move at your own pace.

How long does the “Basic Validation Patterns & Submit Handling” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this React Academy lesson?

Yes. Every React Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

  1. Controlled Forms with Multiple Inputs
  2. Basic Validation Patterns & Submit Handling
  3. Error Messages & Touched/Dirty States (Vanilla)
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