Sign in with Google Plus to my site

I am very new to web development. I searched the login with google plus and found some good tutorials. But they seem to be very old (most of them since 2011). Why?

I tried under the pieces of code.

<script type="text/javascript" language="javascript">    
   $("#packagesGrid").load('https://www.googleapis.com/oauth2/v1/userinfo?alt=json&access_token=ya29.ahes6zt9yv2qaeej5ycn21fn9maokp15scwqkcal3guqxxez7odtjg&token_type=bearer&expires_in=3600');    
</script>

I just manually copied the token into the jQuery download function url. But nothing is populated on the page.