JS 通过系统时间限定动态添加 select option的实例代码

<select id="myselect1"> <option value="">― ―</option> <option value="2015级">2015级</option> <option value="2014级">2014级</option> <option value="2013级">2013级</option> <option value="2012级">2012级</option></select><br><br><select id="myselect2"> <option value="">― ―</option> <option value="2015级">2015级</option> <option value="2014级">2014级</option> <option value="2013级">2013级</option> <option value="2012级">2012级</option></select> var time = new Date(); var month=time.getMonth()+1; var day=time.getDay(); if(month>5&&day>1){  var objSelect=document.getElementById("myselect2");  objSelect.options.add(new Option("2016级", "2016级"),1);  objSelect.options.remove(5); } if(month>7&&day>1){  var objSelect=document.getElementById("myselect1");  objSelect.options.add(new Option("2016级", "2016级"),1);  objSelect.options.remove(5); }