Returns true if client-side validation on the form is successful. Any invalid fields will be
marked as invalid. If you only want to determine overall form validity without marking anything,
use {@link #hasInvalidField} instead.
@return {Boolean}
function() {
        var me = this,
            invalid;
        Ext.suspendLayouts();
        invalid = me.getFields().filterBy(function(field) {
            return !field.validate();
        });
        Ext.resumeLayouts(true);
        return invalid.length < 1;
    }