未捕获的TypeError：无法读取未定义的属性“name”

Question

I tried to fetch data using facebook api into form inputs. Now, everything went just fine until I tried to also fetch the location of the current user.

If the current user have shared his location (Where he is living), then I get no problems. However, if the user hasn't shared his location on facebook, I am getting an error: Uncaught TypeError: Cannot read property 'name' of undefined

Here is the code I've been using. If you have any idea how to solve it, please comment here :)

<div id="fb-root"></div>
<script>
  // Additional JS functions here
  window.fbAsyncInit = function() {
    FB.init({
      appId      : '*******', // App ID
      status     : true, // check login status
      cookie     : true, // enable cookies to allow the server to access the session
      xfbml      : true  // parse XFBML
    });

    FB.getLoginStatus(function(response) {
  if (response.status === 'connected') {

    FB.api('/me', function(response) {
  document.getElementById("user_login").value="FB - " + response.username;
  document.getElementById("user_email").value=response.email;
  document.getElementById("first_name").value=response.first_name;
  document.getElementById("last_name").value=response.last_name;
  document.getElementById("user_url").value=response.link;
  document.getElementById("fbid").value=response.id;
  if(response.location !== 'undefined')
  {
    document.getElementById("location").value=response.location.name;
    alert(response.location.name);
  }
  document.getElementById("registerform").submit();

});

  } else if (response.status === 'not_authorized') {
    alert('error');
  } else {
    alert('Please Log In!');
  }
 });

  };

  // Load the SDK Asynchronously
  (function(d){
     var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
     if (d.getElementById(id)) {return;}
     js = d.createElement('script'); js.id = id; js.async = true;
     js.src = "//connect.facebook.net/en_US/all.js";
     ref.parentNode.insertBefore(js, ref);
   }(document));
</script>

Answer 1

On this line:

if(response.location !== 'undefined')

...you're checking if response.location is not the string "undefined" . Since undefined is not the string "undefined" , the condition is true. Then you try to use response.location.name and as response.location is undefined , you get the error.

You probably meant either:

if(response.location)

or

if(typeof response.location !== 'undefined')