Facebook登录按钮javasdk出错

Question

我使用该代码生成访问令牌与facebook jssdk并使用pre将生成的代码插入到同一个文件中，但它不起作用

       <fb:login-button scope="offline_access, manage_pages">Grant offline_access</fb:login-button>
<h1>Access Token:</h1>
<pre id="access-token"></pre>

<script>
var
  pre         = document.getElementById('access-token'),
  showSession = function(response) {
    var html = 'Not Connected';
    if (response.authResponse) {
      html = response.authResponse.accessToken;
    }
    pre.innerHTML = html;
  };
FB.getLoginStatus(function(response) {
  showSession(response);
  FB.Event.subscribe('auth.sessionChange', showSession);
});
</script>

同样单词“Not Connected：未在页面中显示

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