How can I use the selected option value of a select element in Pug/Jade template

Question

I have this select in Pug/Jade

select.form-select.col-xs-12.col-sm-12(id='selState1', onClick='+setState(selState1.value)')
                  option(value='selState1', name='selState1',id='selState1') Enter state
                  each state in nigeria.states()
                    option(value='state') #{state} 

Now I need to use the value of the selected option as a parameter in function nigeria.lgas() that generates the options for another select

I have done

 select.form-select.col-xs-12.col-sm-12(id='selLG1', name='selLG1')
                  option.active(value='selLG') Enter Local Government
                    each lg in nigeria.lgas(selState1.value)                      
                      option(value=lg) #{lg}

I get the error 'selState1 is not defined'