NodeJS, Facebook GraphAPI: exchange token for access_token

I'm looking into "exchange code for access token" section in nodejs package's documentation.

In the first sample code snippet, it mentions code: 'code'.

FB.api('oauth/access_token', {
    client_id: 'app_id',
    client_secret: 'app_secret',
    redirect_uri: 'http://ift.tt/1zSRfcH',
    code: 'code'

My understanding of this is to get a value to replace 'code'. To get the value, I refer to the 2nd sample code snippet where the author teaches how to extract code out of an URL. However, the URL is predefined with a value.

var urlToParse = 'http://ift.tt/1M9xnbO';

I'm not sure how to get that URL. Could anyone advise?