What Is Form Validation?
When you enter data, the browser or server will check that it is in the right format and valid for the application. Validation done in the browser is called client-side form validation; if the server does it, it is called server-side form validation. This section presents built-in client-side form validation. The last example in this section shows you how to validate forms without a built-in API using JavaScript and the DOM.
Different types of client-side validation
There are two different types of client-side validation that you'll encounter on the web:
- Built-in form validation uses HTML form validation features, which we've discussed in many places throughout this module. This validation generally doesn't require much JavaScript. Built-in form validation has better performance than JavaScript, but it is not as customizable as JavaScript validation.
- JavaScript validation is coded using JavaScript. This validation is completely customizable, but you need to create it all (or use a library).