jsp 日历的源码(2)

        }

        display_month ( form );

    }

    function preceding_month ( form ) {

        var month_selected = form.monthList.selectedIndex;

        var year_selected = form.yearList.selectedIndex;

        if ( !month_selected && !year_selected )  {

            error ();

            return;

        }

        if ( month_selected > 0 )

            month_selected --;

        else {

            month_selected = 11;

            year_selected --;

        }

        form.monthList[month_selected].selected = true;

        form.yearList[year_selected].selected = true;

        display_month ( form );

    }

    function following_month ( form ) {

        var month_selected = form.monthList.selectedIndex;

        var year_selected = form.yearList.selectedIndex;

        if ( month_selected >= ( form.monthList.length - 1 ) && year_selected >= ( form.yearList.length - 1 ) ) {

            error ();

            return;

        }

        if ( month_selected < 11 )

            month_selected ++;

        else {

            month_selected = 0;

            year_selected ++;

        }

        form.monthList[month_selected].selected = true;

        form.yearList[year_selected].selected = true;

        display_month ( form );

    }

    function set_month_year_now ()   {

        var form = document.calendar;