How To Clear All fields except Mandatory ones

[#1]

In My app i want to Clear All selected Fields except for Year and Month.

I have tried these, but nothing is working :

A. In the extension when i use app.clearAll() , its clearing all the fields including Year and Month

B. app.field('Year').clearOther(true);

    app.field('Month').clearOther(true);

   Year Field remain selected, but is clearing Month Field, along with other fields.

C. app.field('Year').lock();

    app.field('Month').lock();

    app.field('Year').clearOther(false);

    app.field('Month').clearOther(false);

     Year Field remain selected, but is clearing Month Field, along with other fields.