Detailed explanation of the use of three ajax parsing modes

This time I will bring you a detailed explanation of the use of the three ajax parsing modes. What are the precautions when using the three ajax parsing modes. The following is a practical case, let's take a look.

1. JSON format in Ajax

html code:

 <input>
 <script>
  var btn = document.getElementById("btn");
  btn.onclick = function(){
    var xhr = getXhr();
    xhr.open("post","10.php");
    xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    /*
     * 在客户端如何构建JSON格式
     * * 构建符合JSON格式的字符串
     */
    var user = &#39;{"name":"zhangwuji","pwd":"123456"}&#39;;
    xhr.send("user="+user);
    xhr.onreadystatechange = function(){
      if(xhr.readyState==4&&xhr.status==200){
        var data = xhr.responseText;
        /*
         * 使用eval()函数进行转换
         * * 使用"()"将其包裹,eval()函数强制将其转换为JSON格式(javascript代码)
         * * 不使用"()"将其包裹,eval()函数将其识别为一个空的代码块
         */
        var json = eval("("+data+")");
        console.log(json);
      }
    }
  }
  function getXhr(){
    var xhr = null;
    if(window.XMLHttpRequest){
      xhr = new XMLHttpRequest();
    }else{
      xhr = new ActiveXObject("Microsoft.XMLHttp");
    }
    return xhr;
  }
 </script>
 

PHP code：

<?php   // 接收客户端发送的请求数据
  $user = $_POST[&#39;user&#39;];
  // 就是一个JSON格式的string字符串
  //var_dump($user);
  $json_user = json_decode($user,true);
  //var_dump($json_user[&#39;name&#39;]);
  $json = &#39;{"a":1,"b":2,"c":3,"d":4,"e":5}&#39;;
  //var_dump(json_decode($json));
  // 响应数据符合JSON格式的字符串
  // 1. 手工方式构建
  //echo &#39;{"name":"zhouzhiruo","pwd":"123456"}&#39;;
  // 2. 使用json_encode()函数
  echo json_encode($json_user);
?>

二 XML format in Ajax

html page:

   
 <input>
 <script>
  var btn = document.getElementById("btn");
  btn.onclick = function(){
    // 实现Ajax的异步交互
    var xhr = getXhr();
    xhr.open("post","07.php");
    xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    /*
     * 如何构建符合XML格式的请求数据
     * * 注意
     *  * 请求数据的格式 - key=value 不能改变的
     * * 将value值构建成符合XML格式的数据
     *  * 数据类型 - 字符串(string)
     *  * 格式符合XML的语法要求
     * * 编写注意
     *  * 定义变量 - 专门构建XML格式的数据
     *  * 在send()方法进行拼串
     */
    var user = "<user><name>zhangwuji<pwd>123456";
    xhr.send("user="+user);
    xhr.onreadystatechange = function(){
      if(xhr.readyState==4&&xhr.status==200){
        // 接收服务器端的响应数据
        var xmlDoc = xhr.responseXML;
        var nameEle = xmlDoc.getElementsByTagName("name")[0];
        var txtEle = nameEle.childNodes[0];
        console.log(txtEle.nodeValue);
      }
    }
  }
  function getXhr(){
    var xhr = null;
    if(window.XMLHttpRequest){
      xhr = new XMLHttpRequest();
    }else{
      xhr = new ActiveXObject("Microsoft.XMLHttp");
    }
    return xhr;
  }
 </script>
 

PHP page code:

<?php   // 接收客户端发送的请求数据
  $user = $_POST[&#39;user&#39;];//符合XML格式要求的string类型
  //var_dump($user);
  // 创建DOMDocument对象
  $doc = new DOMDocument();
  // 调用loadXML()方法
  $result = $doc->loadXML($user);
  //var_dump($doc);
  // 如何构建符合XML格式的数据
  /* 修改响应头的Content-Type值为"text/xml"
  header('Content-Type:text/xml');
  echo $user;// 符合XML格式的string类型
  */
  header('Content-Type:application/xml');
  echo $doc->saveXML();
?>

三 HTML format in Ajax

HTML page:

  
 <select>
  <option>请选择</option>
  <option>山东省</option>
  <option>辽宁省</option>
  <option>吉林省</option>
 </select>
 <select>
  <option>请选择</option>
 </select>
 <script>
  /*
   * 需要思考哪些事情?
   * * 在什么时候执行Ajax的异步请求?
   *  * 当用户选择具体的省份信息时
   */
  // 1. 为id为province元素绑定onchange事件
  var provinceEle = document.getElementById("province");
  provinceEle.onchange = function(){
    // 清空
    var city = document.getElementById("city");
    var opts = city.getElementsByTagName("option");
    for(var z=opts.length-1;z>0;z--){
      city.removeChild(opts[z]);
    }
    if(provinceEle.value != "请选择"){
      // 2. 执行Ajax异步请求
      var xhr = getXhr();
      xhr.open("post","06.php");
      xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
      xhr.send("provcince="+provinceEle.value);
      xhr.onreadystatechange = function(){
        if(xhr.readyState==4&&xhr.status==200){
          // 接收服务器端的数据内容
          var data = xhr.responseText;
          // data是字符串,转换为数组
          var cities = data.split(",");
          for(var i=0;i<cities.length;i++){
            var option = document.createElement("option");
            var textNode = document.createTextNode(cities[i]);
            option.appendChild(textNode);
            city.appendChild(option);
          }
        }
      }
    }
  }
  // 定义创建XMLHttpRequest对象的函数
  function getXhr(){
    var xhr = null;
    if(window.XMLHttpRequest){
      xhr = new XMLHttpRequest();
    }else{
      xhr = new ActiveXObject("Microsoft.XMLHttp");
    }
    return xhr;
  }
 </script>
 

php page:

<?php   // 用于处理客户端请求二级联动的数据
  // 1. 接收客户端发送的省份信息
  $province = $_POST[&#39;provcince&#39;];
  // 2. 判断当前的省份信息,提供不同的城市信息
  switch ($province){
    case &#39;山东省&#39;:
      echo &#39;青岛市,济南市,威海市,日照市,德州市&#39;;
      break;
    case &#39;辽宁省&#39;:
      echo &#39;沈阳市,大连市,铁岭市,丹东市,锦州市&#39;;
      break;
    case &#39;吉林省&#39;:
      echo &#39;长春市,松原市,吉林市,通化市,四平市&#39;;
      break;
  }
  // 服务器端响应的是字符串
?>

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!

Recommended reading:

Detailed explanation of Ajax and $.ajax instances

Adjustment of ajax execution order in jquery

Ajax implements loading waiting effect to improve user experience

The above is the detailed content of Detailed explanation of the use of three ajax parsing modes. For more information, please follow other related articles on the PHP Chinese website!