How can I implement asynchronous validation in my web application?

How can I implement asynchronous validation in my web application?

Asynchronous validation allows you to validate user input without blocking the UI. You can use AJAX calls to check data against the server.

Can you give me an example of how to do that with JavaScript?

Sure! You can use the Fetch API to send a request to your server when the user types in a field. For example:

const inputField = document.getElementById('username');

inputField.addEventListener('blur', async () => {
    const response = await fetch(`/validate-username?username=${inputField.value}`);
    const result = await response.json();
    if (!result.isValid) {
        // Show error message
    }
});

What if I want to validate multiple fields at once?

You can create a function that validates all fields on form submission or on specific events. Just gather the values and send them in a single request.