var date=document.getElementById("dataname").value; var d = new Date(); d.setYear(parseInt(date.substring(0,4),10)); d.setMonth(parseInt(date.substring(5,7)-1,10)); d.setDate(parseInt(date.substring(8,10),10));
var numyue; var newdateString=""; var rtl=document.getElementById("rtl"); var index=rtl.selectedIndex;
var d = new Date();
d.setYear(parseInt(date.substring(0,4),10));
d.setMonth(parseInt(date.substring(5,7)-1,10));
d.setDate(parseInt(date.substring(8,10),10));
var numyue;
var newdateString="";
var rtl=document.getElementById("rtl");
var index=rtl.selectedIndex;
if(index==0){
alert("请选择月份");
}else{
d.setMonth(d.getMonth()+index);
if(d.getMonth()>11){
d.setYear(d.getYear()+1);
d.setMonth(d.getMonth()+index);
newdateString=d.getYear()+"-"+d.getMonth()+"-"+d.getDate();
}else{
if(d.getMonth()==11){
numyue=12;
newdateString=d.getYear()+"-"+numyue+"-"+d.getDate();
}else{
d.setMonth(d.getMonth()+1);
newdateString=d.getYear()+"-"+d.getMonth()+"-"+d.getDate();
}
}
}
document.getElementById("newdataname").value=newdateString;
<option>请选择月份</option>
<option>一个月</option>
<option>二个月</option>
<option>三个月</option>
<option>四个月</option>
<option>五个月</option>
<option>六个月</option>
</select><br/>
<input id="dataname" type="text" value="" />
<input type="button" value="取值" onclick="getselectvalue()"/>
<input id="newdataname" type="text"/>
</body>
</html>