How to update only one field using UI action

Hi ,

I am trying to create an UI action to update only one field. I tried using the below code 

function saveDesc() {
    var desc = g_form.getValue('description');
    g_form.setValue('description', desc);
    gsftSubmit(null, g_form.getFormElement(), 'save_dec'); 
    action.setRedirectURL(current);
}

 Action Name  : save_dec

I am bale to save if i added the value of the description in the setvalue method. But if I am trying to get and set it is not working as expected. and after this script the page should be redirected to the same form page.

Can someone help me out.

Thanks.