HTML DOM Input Radio required property

The HTML DOM input radio required property is associated with the required attribute of an <input> element. The required property is used for setting and returning if it is necessary to check some radio button or not before the form is submitted to the server. This allows the form to not submit if a radio button with required attribute is left unchecked by the user.

Syntax

Following is the syntax for −

Setting the required property.

radioObject.required = true|false

Here, true represents the radio button must be checked while false represents its optional to check the radio button before submitting the form.

Example

Let us look at an example for the input radio required property −

<!DOCTYPE html>
<html>
<body>
<h1>Radio required property</h1>
<form style="border:solid 1px green;padding:5px" action="/Sample_page.php">
FRUIT:
<input type="radio" name="fruits" id="Mango" required>Mango
<br><br>
<input type="submit">
</form>
<button type=”button” onclick="checkReq()">CHECK</button>
<p id="Sample"></p>
<script>
   function checkReq() {
      var Req=document.getElementById("Mango").required;
      if(Req==true)
         document.getElementById("Sample").innerHTML="The radio button must be checked before
         submitting";
      else
         document.getElementById("Sample").innerHTML="The radio button is optional and can be
         left unchecked by the user";
   }
</script>
</body>
</html>

Output

This will produce the following output −

HTML DOM Input Radio required property

On clicking the CHECK button −

HTML DOM Input Radio required property

On clicking the “Submit” button without the radio button being checked −

HTML DOM Input Radio required property

In the above example −

We have first created an input radio button with id “Mango”, name “fruits” and required attribute set to true. The radio button contained inside a form which has action=”Sample_page.php” for specifying where to submit the form data when clicked on the submit button. The form also has an inline style applied to it −

<form style="border:solid 1px green;padding:5px" action="/Sample_page.php">
FRUIT:
<input type="radio" name="fruits" id="Mango" required>Mango
<br><br>
<input type="submit">
</form>

We have then created a button CHECK that will execute the checkReq() method on being clicked upon by the user.

<button type=”button” onclick="checkReq()">CHECK</button>

The checkReq() method uses the getElementById() method to get the input element with type radio and get its required property, which in our case returns true. The returned boolean value is assigned to a variable Req and based on the returned value whether it is true or false we display appropriate message in the paragraph with id “Sample” using its innerHTML property −

function checkReq() {
   var Req=document.getElementById("Mango").required;
   if(Req==true)
      document.getElementById("Sample").innerHTML="The radio button must be checked before submitting";
   else
      document.getElementById("Sample").innerHTML="The radio button is optional and can be left unchecked by the user";
}