Driver code
var head1 = null ; head1 = push ( head1 , 20 ) ; head1 = push ( head1 , 5 ) ; head1 = push ( head1 , 15 ) ; head1 = push ( head1 , 10 ) ; var head2 = null ; head2 = push ( head2 , 10 ) ; head2 = push ( head2 , 2 ) ; head2 = push ( head2 , 15 ) ; head2 = push ( head2 , 8 ) ; document . write ( firstCommon ( head1 , head2 ) ) ;