When running in a SharePoint-Hosted App, you can easily receive the FormDigestValue by executing ShareCoffee.Commons.getFormDigest() which is very easy.

However, if you’re executing queries from a plain HTML page sitting in your SharePoint-Hosted App  - or in the case, you’re running in an Office Add-In -  you can ask for a FormDigestValue using ShareCoffee’s REST interface. The following sample code shows how to receive the FormDigestValue from within a plain HTML Page using AngularJS.

$http(ShareCoffee.REST.build.create.for.angularJS({ url: 'contextinfo'}))
   // access FormDigestValue
   // this is good for single time use. 
   var formDigestValue = data.d.GetContextWebInformation.FormDigestValue;
   // if you need the form-digest-value for more than a single call,
   // go and store it in ShareCoffee.Commons.formDigestValue like shown here:
   ShareCoffee.Commons.formDigestValue = data.d.GetContextWebInformation.FormDigestValue;
   console.log("Error loading Context Info");

In the case, you’re writing your App in CoffeeScript (which is awesome :D) the code looks like the following.

$http(ShareCoffee.REST.build.create.for.angularJS {url: 'contextinfo'})
  # great for single time use
  formDigestValue = data.d.GetContextWebInformation.FormDigestValue
  # use this for page instace wide usages
  ShareCoffee.Commons.formDigestValue = data.d.GetContextWebInformation.FormDigestValue
  console.log "error while loading contextinfo"