参考这个

https://help.fanruan.com/finereport10.0/doc-view-1992.html

写在单选按钮的状态改变事件：pDate1和pDate2是日期控件名字

var frm=this.options.form;

var nowDate = new Date();

var sel = this.getValue();

if(sel =="周"){ //周一

var week = nowDate.getDay()==0?7:nowDate.getDay();

     nowDate.setDate(nowDate.getDate()- week + 1 );

    frm.getWidgetByName("pDate1").setValue(nowDate);

    frm.getWidgetByName("pDate2").setValue(nowDate);

}

else if(sel == "月"){ //月初

    var nowMonth = nowDate.getMonth(); 

    var nowYear = nowDate.getFullYear(); 

    var monthStartDate = new Date(nowYear, nowMonth, 1); 

    frm.getWidgetByName("pDate1").setValue(monthStartDate);

    frm.getWidgetByName("pDate2").setValue(monthStartDate);

}

else if(sel == "日") {    //今天

    frm.getWidgetByName("pDate1").setValue(nowDate);

    frm.getWidgetByName("pDate2").setValue(nowDate);

}