The hidden field is by definition 'invisible', so there isn't a lot to see. However, it can be useful to keep an id :
var exampleDiv = Y.one('#container1');
var group = new Y.inputEx.Group({
fields: [
{ type: 'hidden', name: 'id', value: 12 },
{ type: 'hidden', name: 'lastname', value: 'Scott' },
{ type: 'string', name: 'firstname', label: 'Firstname', required: true, value:'James'}
],
parentEl: exampleDiv
});
var button=inputEx.cn('button',null,null, 'Get Value');
exampleDiv.appendChild(button);
Y.one(button).on('click', function(){ alert(Y.JSON.stringify(group.getValue()) ); });
Note that <hiddenFieldInstance>.getValue() returns the value as stored, without type casting (we store an integer -> we get an integer).
However, when the form is submitted via a 'submit' button, the hidden value is sent as 'string' whatever its datatype was... (we store 12, we submit "12").
This is a limitation of the classic HTML form submit. To circumvent the problem, use an ajax submit of the form (which relies on getValue) : see form examples.