如何返回访问令牌facebook？

Question

I don't know how to sync in api FB.login and here is my code:

function getAccesToken(){
    var access_token = "";
    FB.login(function(response) {
        if (response.authResponse) {
             access_token = FB.getAuthResponse()['accessToken'];

        } else {
            console.log('User cancelled login or did not fully authorize.');
        }
    }, { scope: '' });
    return access_token;
}

when I call function

var access_token = getAccessToken();

but it return empty string. How can I fix it to be synchronous?

Answer 1

You can't make this synchronous - and it would be extremely bad practice if you could. Instead, call a function in the FB.login callback handler that contains the access token. Try this:

function getAccesToken() {
    FB.login(function(response) {
        if (response.authResponse) {
             loginComplete(FB.getAuthResponse()['accessToken']);
        } else {
            console.log('User cancelled login or did not fully authorize.');
        }
    }, { scope: '' });
}

function loginComplete(token) {
    console.log(token);
    // do something here, now the user is logged in...
}

Answer 2

FB.login needs to be called on user interaction (mouse click) and you have to use the callback function of FB.login to get the Access Token asynchronously - the Access Token will be in the response value. For example:

document.getElementById('loginBtn').addEventListener('click', function() {
    FB.login(function(response) {
        if (response.authResponse) {
            doSomethingWithTheToken(response.authResponse.accessToken);
        }
    }, {scope: 'email,public_profile', return_scopes: true});
}, false);

function doSomethingWithTheToken(token) {
    console.log(token);
}

Source (and a lot more information about the JavaScript SDK): http://www.devils-heaven.com/facebook-javascript-sdk-login/