//index.js
var fb = require('com.ti.facebook');

function doClick(e)
{
    if (!fb.loggedIn)
        Ti.API.log('not logged in')
    else
        Ti.API.log('logged in')

    fb.permissions = ['public_profile', 'email', 'user_friends'];
    fb.addEventListener('login', function(e) {
        if(e.success) {
            Ti.API.log('login successful!!')
        } else if (e.cancelled) {
            Ti.API.log('cancelled')
        } else if (e.error) {

            if (Ti.Platform.name === 'iPhone OS') {
                var loginAlert = Ti.UI.createAlertDialog({title: 'Login Error'});
                if (e.error.indexOf('OTHER:') !== 0){
                } else {
                   Ti.API.log('error else')
                }
            } else {
                Ti.API.log('error else')
            }
        } else {
             Ti.API.log('other error...')
        }
    });
    fb.initialize(0);

    var win = Ti.UI.createWindow();
    win.fbProxy = fb.createActivityWorker({lifecycleContainer: win })

    var btn = Ti.UI.createButton({ Title : 'facebook login' });
    btn.addEventListener('click', function(e)
    {
        Ti.API.log('facebook login clicked')
        fb.authorize();
    })
    win.add(btn);
    win.open();

}

$.win.open();



<!-- index.xml -->
<Alloy>
        <Window class="container">
                <Label id="label" onClick="doClick">Facebook Login</Label>
        </Window>
</Alloy>