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How to use JS+AJAX to make three-level linkage

php中世界最好的语言Original: 2018-06-01 11:19:341435browse

This time I will show you how to use JS AJAX to make three-level linkage, and what are the precautions for using JS AJAX to make three-level linkage. The following is a practical case, let's take a look.

js The implementation code of three-level linkage is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>js原生ajax</title>
</head>
<body>
  <select name="sel1">
    <option value="" >-请选择 省/直辖市/自治区-</option>
  </select>
  <select name="sel2">
    <option value="" >-请选择 市-</option>
  </select>
  <input type="text" value="" id="int"/>
  <script>
    var sel1 = document.getElementsByName('sel1')[0];
    var sel2 = document.getElementsByName('sel2')[0];
    var ints = document.getElementById('int');
    // 创建请求对象
    var a = new XMLHttpRequest();
    // 初始化
    a.open('get','city.json','true');
    // 发送
    a.send();
    //readySate 状态码 交互进行到了哪一步
    //0：请求未初始化
    //1：服务器链接已建立
    //2：请求已经接受
    //3：请求处理中
    //4：请求已经完成，且响应已就绪
    //status 交互是否成功
    a.onreadystatechange = function(){
      if(a.status ==200||a.status == 304){
        if(a.readyState == 4){
          var obj = JSON.parse(a.response);//responseText:获得字符串形式的响应数据。
          var b = obj.城市代码;
          for(var i = 0;i<b.length;i++){
            var nOpt = document.createElement(&#39;option&#39;);
            var nOpt_t =document.createTextNode(b[i].省);
            nOpt.appendChild(nOpt_t);
            sel1.appendChild(nOpt);
            nOpt.value = i;
            console.log(ints.value)
          }
          sel1.onchange = function (){
            var index = sel1.selectedIndex;  //获取select选择的option的下标值
            var va = sel1.options[index].value//获取select第几个option的value值
            var city = b[va].市;    //获取他下边的市
            sel2.options.length = 1;  //清空所有的select下的option的值
            for(var i = 0;i<city.length;i++){
              var nOpt = document.createElement(&#39;option&#39;);
              var nOpt_t =document.createTextNode(city[i].市名);
              nOpt.appendChild(nOpt_t);
              sel2.appendChild(nOpt);
              nOpt.value = i;
              ints.value = "";
            }
          }
          sel2.onchange = function (){
            var sel1v = sel1.value;
            var sel2v = sel2.value;
            var intsi = b[sel1v][&#39;市&#39;][sel2v][&#39;编码&#39;];
            ints.value = intsi;
          }
        }
      }
    }
  </script>
</body>
</html>

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!

How to use JS+AJAX to make three-level linkage

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