Calling FB.login results in the JS SDK attempting to open a popup window. As such, this method should only be called after a user click event, otherwise the popup window will be blocked by most browsers.
FB.login(function(response) {
if (response.authResponse) {
console.log('Welcome! Fetching your information.... ');
FB.api('me', function(response) {
console.log('Good to see you, ' + response.name + '.');
});
} else {
console.log('User cancelled login or did not fully authorize.');
}
});