...as a means to access mobile device contacts? <--that is the short version
In order to use cordova.js, you must also use the Cordova (or PhoneGap) native code wrapper. This is because the two function together in order to create a bridge. You get this when you use PhoneGap Build, the PhoneGap CLI, or the Cordova CLI to build your app.
Furthermore, in order to gain access to contacts, you need an additional plugin: cordova-plugin-contacts.
I'm not sure if that helps you or not -- feel free to ping if not.