Get form field values in javascript execution block

Example function to retrieve a value from a simple field in a request form

 var getFormField (formvalues, fieldname) {
   formvalues.filter(function(fld) { return fld.internallabel === fieldname }).map(function(fld) { return fld.value; }).join("");
 }

 var fieldValue = getFormField(g_forminstance.values, 'fieldname');