JavaScript form validation typically occurs after the form is submitted but before the form data is sent to the server. This allows the client-side script to check the input data and prevent the form from being submitted if the data is invalid.
* Client-Side Validation:
* Before Form Submission: JavaScript validates the form fields after the user attempts to submit the form.
* Prevent Default Submission: If the validation fails, JavaScript can prevent the form from being submitted and display appropriate error messages.
* Usage Example:
document.getElementById("myForm").addEventListener("submit", function(event) { var isValid = true;
// Perform validation checks
if (!isValid) {
event.preventDefault(); // Prevent form submission
alert("Please correct the errors.");
}
});
This example prevents form submission if the validation fails.
References:
* MDN Web Docs on Form Validation
* W3C HTML Specification on Form Submission