A required field validator for a radio button is a programming function that forces the user to select an option in a radio button group before successful submission of a website form. Required field validators can be applied in real time, when the user pushes the submit button, or retroactively after the user has submitted an incomplete form. Required field validators can be applied to all types of data entry fields on a form and aren't limited to radio buttons. Website developers use required field validators when a specific option on a form needs to be completed for the recipient's needs.

HTML Forms and Radio Buttons

HTML forms gather input data from website visitors. Depending on the information the website needs, the site will implement different types of input methods such as text fields, check boxes and radio buttons. Radio buttons let the user select a single option from a predetermined list. The name radio button comes from similar "one choice" buttons that older car radios used. Forms can use multiple radio button groups: the radio buttons are grouped together by the HTML "name" property.

Required and Optional Fields

Some form fields may be required, however not every field may be mandatory. Required field validators are the programming element that determine if a field is required. Many programming languages use required field validators to check user input. HTML supports a required field attribute, but it isn't supported by all browsers. Instead, the form is tied to a script written in JavaScript or jQuery that runs the actual field checking. Web developers can use third-party validation scripts or develop custom scripts.

Value Checking

Validators can check for errors to ensure the user has entered the correct information in the corresponding field. For example, validators can be used to check a field designated for phone numbers to make sure there are enough digits and only digits entered in the field. Since radio buttons select from a list of pre-entered values, validators are typically used to make sure the user has selected an option in the radio button group. However, validators can be used to reject specific radio button options relative to values in other fields on the form.

Required Radio Button Use Cases

Requiring form fields helps the data recipient down the line. Web forms can be used for a variety of things like toggling user preferences on a website, forwarding support email and placing an order. For example, a t-shirt order form may use a radio button to enable the user to select a size. Requiring the radio button selection makes sense because the form recipient needs to know which size shirt to send. The same order form may include an optional radio button question such as "on a scale of one to five, rate your shopping experience."