Use ajax to implement select three-level linkage function

This time I will bring you the use of ajax to implement the select three-level linkage function, and what are the precautions for using ajax to implement the select three-level linkage function. The following is a practical case, let's take a look.

This article uses ajax technology to obtain data from the database and dynamically implement select three-level linkage. The rendering is as follows:

The front-end js code is as follows:

<script></script>
<script>
$(document).ready(function(){
$.ajax({
type:"get",
dataType:"text",
url:"GetItemAction?itemlevel=1",
 success:function(data){
 // 由JSON字符串转换为JSON对象
  var objJSON=eval("("+data+")");
 var len=objJSON.itemInfo.length; 
 var objSelect=document.getElementById("firstlevel");
 for(var i=0;i<len;i++){
 var op=new Option(objJSON.itemInfo[i].itemname,objJSON.itemInfo[i].itemcode);
 objSelect.add(op);
 } 
 },
error: function (XMLHttpRequest, textStatus, errorThrown) { 
   alert(errorThrown); 
  }
});
});
//显示二级分类
function firstlevel_Click(){
var objfirst=document.getElementById("firstlevel");
var index=objfirst.selectedIndex; //选中索引 
var itemcode=objfirst.options[index].value; //选中值
if(itemcode==0){
alert("请选择事件类别");
return;
}
// 删除二级分类保留第一个
var objsecond=document.getElementById("secondlevel");
for(var i=objsecond.options.length-1;i>0;i--){
objsecond.options.remove(i);
}
// 删除三级分类保留第一个
var objthird=document.getElementById("thirdlevel");
for(var i=objthird.options.length-1;i>0;i--){
objthird.options.remove(i);
}
$.ajax({
type:"get",
dataType:"text",
url:"GetItemAction?itemlevel=2&itemcode="+itemcode,
 success:function(data){
 // 由JSON字符串转换为JSON对象
  var objJSON=eval("("+data+")");
 var len=objJSON.itemInfo.length;
 var objSelect=document.getElementById("secondlevel");
 for(var i=0;i<len;i++){
 var op=new Option(objJSON.itemInfo[i].itemname,objJSON.itemInfo[i].itemcode);
 objSelect.add(op);
 } 
 },
error: function (XMLHttpRequest, textStatus, errorThrown) { 
   alert(errorThrown); 
  }
});
}
//显示三级分类
function secondlevel_Click(){
var objsecond=document.getElementById("secondlevel");
var index=objsecond.selectedIndex; //选中索引 
var itemcode=objsecond.options[index].value; //选中值
if(itemcode==0){
alert("请选择事件类别");
return;
}
// 删除三级分类保留第一个
var objthird=document.getElementById("thirdlevel");
for(var i=objthird.options.length-1;i>0;i--){
objthird.options.remove(i);
}
$.ajax({
type:"get",
dataType:"text",
url:"GetItemAction?itemlevel=3&itemcode="+itemcode,
 success:function(data){
 // 由JSON字符串转换为JSON对象
  var objJSON=eval("("+data+")");
 var len=objJSON.itemInfo.length;
 var objSelect=document.getElementById("thirdlevel");
 for(var i=0;i<len;i++){
 var op=new Option(objJSON.itemInfo[i].itemname,objJSON.itemInfo[i].itemcode);
 objSelect.add(op);
 } 
 },
error: function (XMLHttpRequest, textStatus, errorThrown) { 
   alert(errorThrown); 
  }
});
}</script>

Part of the html code

                   

   请选择事件大类         

   请选择事件小类    

   请选择事件类别    

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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