In the <head> of your HTML, include OAuth.js
<script src="/path/to/OAuth.js"></script>
In your Javascript, add this line to initialize OAuth.js
OAuth.initialize('Public key');
To connect your user using facebook, 2 methods:
//Using popup (option 1)
OAuth.popup('facebook', function(err, result) {
//handle error with err
//use result.access_token in your API request
});//Using redirection (option 2)
OAuth.redirect('facebook', "callback/url");In callback url :
OAuth.callback('facebook', function(err, result) {
//handle error with err
//use result.access_token in your API request
});More information in oauth.io documentation