v-bind绑定

我觉得写得没问题呀，为啥v-bind不起作用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>属性绑定和双向数据绑定</title>
</head>
<body>
    <div id="divid">
        <div v-bind:title="title">hello world</div>
    </div>

    <script>
        new Vue({
            el:"#divid",
            data: {
                title: "this is hello world"
            }
        })
    </script>

</body>
</html>