Sets or gets whether an input element is required to have a value.
Setting the required property to true causes the
element to be invalid if it
doesn't contain a value. Setting it to false allows the element to be
valid even if it doesn't contain a value. The validity of the element
can be checked using its validity
property.
Getting the value of the required property returns whether the element
is required.
You can also set an input element to be required by using the element's Settings panel in the Editor.