1.新建一个select.html
1 <html><head></head><body><select id="1"> 2 <option value="东风本田">东风本田</option> 3 <option value="广汽本田">广汽本田</option> 4 <option value="一汽大众">一汽大众</option> 5 <option value="上海大众">上海大众</option> 6 </select></body></html>
2.js操作打开下拉框
1 function openselect(){ 2 var select1=document.getElementById(1); 3 var selectlength = select1.length; 4 select1.size = selectlength; 5 select1.style = "height:100%"; 6 return ''} 7 openselect();
3.选择其中一个选项
1 function selectone(){ 2 var selectoption = document.evaluate('//*[@id="1"]/option[3]', document).iterateNext(); 3 selectoption.parentNode.size = 1; 4 selectoption.parentNode.style = "none"; 5 selectoption.selected = true; 6 return '';} 7 selectone();
4.执行事件
let evt = document.createEvent('HTMLEvents'); evt.initEvent('change', false, true);//页面的下拉框change事件
selectoption.parentNode.dispatchEvent(evt);