Html radio this value

HTML DOM Input Radio Object

The Input Radio object represents an HTML element with type=»radio».

Access an Input Radio Object

You can access an element with type=»radio» by using getElementById():

Example

Tip: You can also access by searching through the elements collection of a form.

Create an Input Radio Object

You can create an element with type=»radio» by using the document.createElement() method:

Example

Input Radio Object Properties

Property	Description
autofocus	Sets or returns whether a radio button should automatically get focus when the page loads
checked	Sets or returns the checked state of a radio button
defaultChecked	Returns the default value of the checked attribute
defaultValue	Sets or returns the default value of a radio button
disabled	Sets or returns whether the radio button is disabled, or not
form	Returns a reference to the form that contains the radio button
name	Sets or returns the value of the name attribute of a radio button
required	Sets or returns whether the radio button must be checked before submitting a form
type	Returns which type of form element the radio button is
value	Sets or returns the value of the value attribute of the radio button

Standard Properties and Events

The Input Radio object also supports the standard properties and events.

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Html radio this value

Only one radio button in a given group can be selected at the same time. Radio buttons are typically rendered as small circles, which are filled or highlighted when selected.

Try it

They are called radio buttons because they look and operate in a similar manner to the push buttons on old-fashioned radios, such as the one shown below.

Note: Checkboxes are similar to radio buttons, but with an important distinction: radio buttons are designed for selecting one value out of a set, whereas checkboxes let you turn individual values on and off. Where multiple controls exist, radio buttons allow one to be selected out of them all, whereas checkboxes allow multiple values to be selected.

Value

The value attribute is a string containing the radio button’s value. The value is never shown to the user by their user agent. Instead, it’s used to identify which radio button in a group is selected.

Defining a radio group

A radio group is defined by giving each of radio buttons in the group the same name . Once a radio group is established, selecting any radio button in that group automatically deselects any currently-selected radio button in the same group.

You can have as many radio groups on a page as you like, as long as each has its own unique name .

For example, if your form needs to ask the user for their preferred contact method, you might create three radio buttons, each with the name property set to contact but one with the value email , one with the value phone , and one with the value mail . The user never sees the value or the name (unless you expressly add code to display it).

The resulting HTML looks like this:

form> fieldset> legend>Please select your preferred contact method:legend> div> input type="radio" id="contactChoice1" name="contact" value="email" /> label for="contactChoice1">Emaillabel> input type="radio" id="contactChoice2" name="contact" value="phone" /> label for="contactChoice2">Phonelabel> input type="radio" id="contactChoice3" name="contact" value="mail" /> label for="contactChoice3">Maillabel> div> div> button type="submit">Submitbutton> div> fieldset> form> 

Here you see the three radio buttons, each with the name set to contact and each with a unique value that uniquely identifies that individual radio button within the group. They each also have a unique id , which is used by the element’s for attribute to associate the labels with the radio buttons.

You can try out this example here:

Data representation of a radio group

When the above form is submitted with a radio button selected, the form’s data includes an entry in the form contact=value . For example, if the user clicks on the «Phone» radio button then submits the form, the form’s data will include the line contact=phone .

If you omit the value attribute in the HTML, the submitted form data assigns the value on to the group. In this scenario, if the user clicked on the «Phone» option and submitted the form, the resulting form data would be contact=on , which isn’t helpful. So don’t forget to set your value attributes!

Note: If no radio button is selected when the form is submitted, the radio group is not included in the submitted form data at all, since there is no value to report.

It’s fairly uncommon to actually want to allow the form to be submitted without any of the radio buttons in a group selected, so it is usually wise to have one default to the checked state. See Selecting a radio button by default below.

Let’s add a bit of code to our example so we can examine the data generated by this form. The HTML is revised to add a block to output the form data into:

form> fieldset> legend>Please select your preferred contact method:legend> div> input type="radio" id="contactChoice1" name="contact" value="email" /> label for="contactChoice1">Emaillabel> input type="radio" id="contactChoice2" name="contact" value="phone" /> label for="contactChoice2">Phonelabel> input type="radio" id="contactChoice3" name="contact" value="mail" /> label for="contactChoice3">Maillabel> div> div> button type="submit">Submitbutton> div> fieldset> form> pre id="log">pre> 

Then we add some JavaScript to set up an event listener on the submit event, which is sent when the user clicks the «Submit» button:

const form = document.querySelector("form"); const log = document.querySelector("#log"); form.addEventListener( "submit", (event) =>  const data = new FormData(form); let output = ""; for (const entry of data)  output = `$output>$entry[0]>=$entry[1]>\r`; > log.innerText = output; event.preventDefault(); >, false, ); 

Try this example out and see how there’s never more than one result for the contact group.

Additional attributes

In addition to the common attributes shared by all elements, radio inputs support the following attributes.

A Boolean attribute which, if present, indicates that this radio button is the default selected one in the group.

Unlike other browsers, Firefox by default persists the dynamic checked state of an across page loads. Use the autocomplete attribute to control this feature.

Using radio inputs

We already covered the fundamentals of radio buttons above. Let’s now look at the other common radio-button-related features and techniques you may need to know about.

Selecting a radio button by default

To make a radio button selected by default, you include checked attribute, as shown in this revised version of the previous example:

form> fieldset> legend>Please select your preferred contact method:legend> div> input type="radio" id="contactChoice1" name="contact" value="email" checked /> label for="contactChoice1">Emaillabel> input type="radio" id="contactChoice2" name="contact" value="phone" /> label for="contactChoice2">Phonelabel> input type="radio" id="contactChoice3" name="contact" value="mail" /> label for="contactChoice3">Maillabel> div> div> button type="submit">Submitbutton> div> fieldset> form> 

In this case, the first radio button is now selected by default.

Note: If you put the checked attribute on more than one radio button, later instances will override earlier ones; that is, the last checked radio button will be the one that is selected. This is because only one radio button in a group can ever be selected at once, and the user agent automatically deselects others each time a new one is marked as checked.

Providing a bigger hit area for your radio buttons

Beyond accessibility, this is another good reason to properly set up elements on your forms.

Validation

Radio buttons don’t participate in constraint validation; they have no real value to be constrained.

Styling radio inputs

The following example shows a slightly more thorough version of the example we’ve seen throughout the article, with some additional styling, and with better semantics established through use of specialized elements. The HTML looks like this:

form> fieldset> legend>Please select your preferred contact method:legend> div> input type="radio" id="contactChoice1" name="contact" value="email" checked /> label for="contactChoice1">Emaillabel> input type="radio" id="contactChoice2" name="contact" value="phone" /> label for="contactChoice2">Phonelabel> input type="radio" id="contactChoice3" name="contact" value="mail" /> label for="contactChoice3">Maillabel> div> div> button type="submit">Submitbutton> div> fieldset> form> 

The CSS involved in this example is a bit more significant:

html  font-family: sans-serif; > div:first-of-type  display: flex; align-items: flex-start; margin-bottom: 5px; > label  margin-right: 15px; line-height: 32px; > input  appearance: none; border-radius: 50%; width: 16px; height: 16px; border: 2px solid #999; transition: 0.2s all linear; margin-right: 5px; position: relative; top: 4px; > input:checked  border: 6px solid black; > button, legend  color: white; background-color: black; padding: 5px 10px; border-radius: 0; border: 0; font-size: 14px; > button:hover, button:focus  color: #999; > button:active  background-color: white; color: black; outline: 1px solid black; > 

Most notable here is the use of the appearance property (with prefixes needed to support some browsers). By default, radio buttons (and checkboxes) are styled with the operating system’s native styles for those controls. By specifying appearance: none , you can remove the native styling altogether, and create your own styles for them. Here we’ve used a border along with border-radius and a transition to create a nice animating radio selection. Notice also how the :checked pseudo-class is used to specify the styles for the radio button’s appearance when selected.

Note: If you wish to use the appearance property, you should test it very carefully. Although it is supported in most modern browsers, its implementation varies widely. In older browsers, even the keyword none does not have the same effect across different browsers, and some do not support it at all. The differences are smaller in the newest browsers.

Notice that when clicking on a radio button, there’s a nice, smooth fade out/in effect as the two buttons change state. In addition, the style and coloring of the legend and submit button are customized to have strong contrast. This might not be a look you’d want in a real web application, but it definitely shows off the possibilities.

Technical summary

Specifications

Browser compatibility

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