Forms are used in web pages for the user to enter their required details that further send it to the server for processing. A form is also known as a web form or HTML form. Examples of form use are prevalent in e-commerce websites, online banking, and online surveys.

The data entered into a form needs to be in the right format, and specific fields need to be filled to effectively use the submitted form. Username, password, contact information are some details that are mandatory in ways and thus need to be provided by the user.

HTML is used to create the form, JavaScript to validate the form, and CSS to design the layout of the form.

What is form validation?

Go to any popular site with a registration form, and you will notice that they give you feedback when you don’t enter your data in the format they are expecting. You’ll get messages such as:

– “You can’t leave this field blank.”
– “Please enter your phone number in the format xxx-xxxx.”
– “Please enter a valid email address.”
– “Your password needs to be between 8 and 30 characters long and contain one uppercase letter, one symbol, and a number.”

This is called form validation. When you enter data, the web application checks it to see that the data is correct. If the information is accurate, the app allows the data to be submitted to the server and (usually) saved in a database; if the information isn’t correct, it gives you an error message explaining what needs to be corrected. Form validation can be implemented in different ways.

What are the types of form validation?

– Client-side validation is validation that occurs in the browser before the data has been submitted to the server. Client-side validation is more user-friendly than server-side validation because it gives an instant response. Client-side validation is further subdivided into the following categories:
JavaScript validation is coded using JavaScript. This validation is entirely customizable.

Built-in form validation uses HTML5 form validation features. This validation generally doesn’t require JavaScript. Built-in form validation has better performance than but is not as customizable as, JavaScript.

– Server-side validation is validation that occurs on the server after the data has been submitted. Server-side code is used to validate the data before the data is saved in the database. If the data fails authentication, a response is sent back to the client with corrections that the user needs to make. Server-side validation is not as user-friendly as client-side validation because it doesn’t provide errors until the entire form has been submitted.

In the real world, developers tend to use a combination of client-side and server-side validation.