JavaScript实现ajax发送表单数据

<div><a onclick="show_form();">添加</a></div>
<div class="model hide">
    <form method="post" id="add">
        <input type="text" name="username" placeholder="username">
        <input type="text" name="age"  placeholder="age">
        <input type="radio" name="gender" value="1" checked>男
        <input type="radio" name="gender" value="0">女
        <select name="class">
            {% for cls in classes %}
                <option value="{{ cls.id }}">{{ cls }}</option>
            {% endfor %}
        </select>
        <input type="button" onclick="add_stu();" value="添加">
    </form>
</div>
<div>
    <table border="1">
        <thead>
            <tr>
                <th>ID</th>
                <th>姓名</th>
                <th>年龄</th>
                <th>性别</th>
                <th>班级</th>
                <th>编辑</th>
            </tr>
        </thead>
        <tbody>
            {% for row in students %}
                <tr><td>{{ row.id }}</td>
                    <td>{{ row.username }}</td>
                    <td>{{ row.age }}</td>
                    <td>
                        {% if row.gender %}
                        男
                        {% else %}
                        女
                        {% endif %}
                    </td>
                    <td>{{ row.cls }}</td>
                    <td><a onclick="XhrPostRequest(this);">删除</a>|<a href="/edit_student.html?nid={{ row.id }}">编辑</a></td>
                </tr>
            {% endfor %}
        </tbody>
    </table>
</div>

    function show_form(){
        document.getElementsByClassName("model")[0].className = ‘model‘;
    }

    function GetXhr(){
        if(XMLHttpRequest){
            var Xh = new XMLHttpRequest();
        }else{
            Xh = new ActiveXObject(‘Microsoft.XMLHTTP‘);
        }
        return Xh
    }



    function add_stu(){
        var xhr=GetXhr();

        xhr.onreadystatechange = function(){　　#只要是状态码发生改变就会触发
            var data=xhr.responseText;
            var ret_dict = JSON.parse(data);
            if(xhr.readyState==4){
                alert(ret_dict[‘status‘])
                document.getElementById("add").reset();
                document.getElementsByClassName("model")[0].className += ‘ hide‘;
                document.location.reload()
            }
        }

        //获取text值
        var username=document.getElementsByName("username")[0].value;
        var age = document.getElementsByName(‘age‘)[0].value;
        //var token =document.getElementsByName(‘csrfmiddlewaretoken‘)[0].value;
        var token = "{{ csrf_token }}"
        //获取radio的表单值
        var radio = document.getElementsByName(‘gender‘);
        var gender=null;
        for(i=0;i<radio.length;i++){
            if(radio[i].checked){
                if(i==0)
                    gender=1;
                else
                    gender=0;
            }
        }
        //获取select表单值
        var select=document.getElementsByName(‘class‘)[0]
        var index=select.selectedIndex;
        var sel_id = select[index].value;

        //重组数据
        var data = "username="+username+"&age="+age+"&gender="+gender+"&class="+sel_id+"&csrfmiddlewaretoken="+token;
        xhr.open(‘post‘,‘/add_student.html‘);
　　　　 #请求头一定要设置
        xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded;charset-UTF-8");
        xhr.send(data);
    }