Sets or gets the value of the selected options.
Setting the value property sets the options
with those values to be the selected options. You must set the value
property to values that exist in the options list.
To reset the checkbox group to have no options
selected, set the value property to an empty array, null or undefined.
Getting the value property returns the values of
the currently selected options. If no value is selected, the
value property returns an empty array.
Note: Changing a checkbox group's value in code does not trigger an onChange event.