To set the value of a Action Form dropdown using JQuery

If you place your code in the On Change/Click section of a form field, the following will work:

form.fields.FieldName.value = "AValue";

*Note the value you are setting must match one of the choices in the dropdown

If you are placing your code in a static text field or the initilization section,

you might need to get in-scope to set it. Try the following example

//gets the scope and uses it to set the value

  angular.element($("#dnn931Size")).scope().form.fields.Size.value = '12px';

//Update the UI with the change
  angular.element($("#dnn931Size")).scope().$apply();