原生js中ajax访问的实例详解

function createXmlHttp() {     var xmlHttp;     try { // Firefox, Opera 8.0+, Safari       xmlHttp = new XMLHttpRequest();     }     catch (e) {       try {// Internet Explorer         xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");       }       catch (e) {         try {           xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");         }         catch (e) { }       }     }     return xmlHttp;   }   function infoCheck(){    var ename=document.getElementById("ename").value;    var password=document.getElementById("password").value;    var pwdConfirm=document.getElementById("pwdConfirm").value;    if(password!=pwdConfirm){      alert("两次密码不统一");      return ;    }    //验证登录用户名是否存在，类似的可以验证手机号什么的    // 1.创建异步对象     var xhr = createXmlHttp();     xhr.onreadystatechange = function () {       if (xhr.readyState === 4 && xhr.status === 200) {       //  var data = new Function("return" + xhr.responseText)()//反序列化       var val=xhr.responseText;        if(val==1){          document.getElementById("ch").innerHTML="重新设置名字";          document.getElementById("ename").focus();          return;        }else{          document.getElementById("ch").innerHTML="";        }      }     }     xhr.open("post", 'LoginController/checkEname?ename='+escape(encodeURIComponent(ename)), true);      //发送     xhr.send(null);   } 

  <filter>    <filter-name>encodingFilter</filter-name>    <filter-class>        org.springframework.web.filter.CharacterEncodingFilter      </filter-class>    <init-param>     <param-name>encoding</param-name>     <param-value>utf-8</param-value>    </init-param>    <init-param>     <param-name>forceEncoding</param-name>     <param-value>true</param-value>    </init-param>   </filter>   <filter-mapping>    <filter-name>encodingFilter</filter-name>    <url-pattern>/*</url-pattern>   </filter-mapping>   提交的时候   剩下的 小部分的乱码可以用编码在解码的方式获得正确数据   编码:'LoginController/checkEname?ename='+escape(encodeURIComponent(ename))   解码:try {      String str=URLDecoder.decode(ename, "utf-8");       ename=URLDecoder.decode(ename, "utf-8");    } catch (UnsupportedEncodingException e) {      e.printStackTrace();    }    后面写入数据库的时候乱码问题,我个人先创数据库编码是utf8,项目的编码也是utf-8,避免其他的编码问题发生，在连接数据库的URL也加上url=jdbc:mysql://localhost:3306/ssm?useUnicode=true&characterEncoding=utf8目前碰到的乱码问题已经解决（除开ajax返回数据乱码，这个目前没找到解决方案）

<form action="LoginController/register" method="post" id="form">姓名:<input type="text" name="name" id="name"><br>登录名:<input type="text" name="ename" id="ename" onblur="infoCheck()"> <font id="ch" name="ch"></font><br>密码:<input type="password" name="password" id="password"><br>密码确定:<input type="password" name="pwdConfirm" id="pwdConfirm"><br><input type="button" value="注册" onclick="submitInfo()" ></form>function submitInfo(){    var name=document.getElementById("name").value;    var ename=document.getElementById("ename").value;    var password=document.getElementById("password").value;    var pwdConfirm=document.getElementById("pwdConfirm").value;    //针对空格和制表符的""能做到过滤    name=name.replace(/(^/s*)|(/s*$)/g, "");    ename=ename.replace(/(^/s*)|(/s*$)/g, "");    password=password.replace(/(^/s*)|(/s*$)/g, "");    pwdConfirm=pwdConfirm.replace(/(^/s*)|(/s*$)/g, "");    if(name.length==0||name==" "||name.langth=="undefined") {    //alert(name.langth);    //alert(111);    alert("姓名为必填项");    return ;    }    if(ename.length==0||ename=="  "||ename.langth=="undefined") {    alert("登录名为必填项");    return ;    }    if(password.length==0||password==" "||password.langth=="undefined") {    alert("密码为必填项");    return;    }    if(password!=pwdConfirm){      alert("两次密码不统一");      return ;    }     document.getElementById("form").submit();  }