function  CheckForm()   
{  
var reg1=/^(\d{4})\-(\d{1,2})\-(\d{1,2})$/; 
Degree=form1.elements.length;
for   (i=0;i <Degree;i++) 
{
if (!reg1.test(form1.truetm[i].value)) 
 {
 alert( "日期格式不正确！,正确格式为：2012-12-31"); 
 form1.truetm[i].select();
 form1.truetm[i].focus(); 
return   false; 
 }   
}
return true;
}

alert(/^\d{4}\-\d{1,2}\-\d{1,2}$/.test("2012-12-31"));