Validation checks input before accepting it
Full lesson content unlocks in the student player.
JavaScript Builder Lab · Lesson 8 of 12
Simple Form Validation
Check for missing or weak user input so forms guide people more clearly before submission.
Academy Plus
4 practice exercises
1 homework item
What you will learn
- Explain validation as checking whether input is acceptable before continuing.
- Compare empty, weak, and acceptable form input in beginner-friendly terms.
- Read values, trim text, and apply simple validation checks.
- Use clear feedback messages for invalid and accepted input.
- Describe preventDefault as a way to pause normal form continuation during practice.
Lesson shape
20 minute lesson with 7 sections, 4 exercises, 4 checkpoint questions, and 1 homework submission.
This track requires the Academy Plus plan.
Lesson outline
What this lesson includes
This lesson is available with the Academy Plus membership. Create an account to open the full student player, exercises, quiz, and completion tracking.
Empty input and valid input are different states
Full lesson content unlocks in the student player.
HTML required and JavaScript checks work differently
Full lesson content unlocks in the student player.
Submit events and preventDefault
Full lesson content unlocks in the student player.
Useful beginner validation checks
Full lesson content unlocks in the student player.
Common validation mistakes
Full lesson content unlocks in the student player.
Validation improves the next user action
Full lesson content unlocks in the student player.
Homework
Assignments attached to this lesson
Text response
Open homework
Simple Form Validation: quick check
Write a short beginner explanation of the main idea from Simple Form Validation.
Keep moving
Finish this lesson, then move forward without losing your place.
Use the student player for saved sections, safe practice, quiz progress, and completion tracking.