json内容无法传入

html

 <table border="1">

            <thead>

                <tr>

                    <th>姓名</th>

                    <th>年龄</th>

                    <th>性别</th>

                </tr>

            </thead>

            <tbody>

            </tbody>

        </table>

js

 <script>

            var tbody = document.querySelector('tbody')

            var xhr = new XMLHttpRequest()

            xhr.onload = function(){

            if(xhr.status == 200){

                var data = JSON.parse(xhr.responseText)

                console.log(data)

                for(var i=0;i<data.list.lenght;i++){

                    var tr = document.createElement('tr')

                    for(var attr in data.list[i]){

                        var td = document.createElement('td')

                        td.innerHTML = data.list[i][attr]

                        tr.append(td)

                    }

                    tbody.append(tr)

                }

            }

        }

        xhr.open('GET','/index',true)

        xhr.send()

    </script>

index.js路由

router.get('/index',(ctx,next) => {

  console.log(ctx.request.query)

  ctx.body = {

    errcode : 0,

    errmsg : 'ok',

    list : [

      {"username" : "James","age" : 20,"gender" : "男"},

      {"username" : "Mary","age" : 22,"gender" : "女"},

      {"username" : "Andy","age" : 24,"gender" : "女"}

    ]

  }

})