Uncaught ReferenceError: jsonCallback is not defined

[camsong]

Uncaught ReferenceError: jsonCallback is not defined

[hanxzi]

jsonpCallbackFunction: 'jsonCallback'

[kaidjohnson]

Based on what I see when going to http://opendata.euskadi.eus/contenidos/ds_recursos_turisticos/albergues_de_euskadi/opendata/alojamientos.json, it appears that this service is always going to return the callback as jsonCallback. So the request you want to build is http://opendata.euskadi.eus/contenidos/ds_recursos_turisticos/albergues_de_euskadi/opendata/alojamientos.json?callback=jsonCallback
which means you want to use:

fetchJsonp("http://opendata.euskadi.eus/contenidos/ds_recursos_turisticos/albergues_de_euskadi/opendata/alojamientos.json", { 
  jsonCallbackFunction: 'jsonCallback'
});

Check out https://github.com/camsong/fetch-jsonp#difference-between-jsonpcallback-and-jsoncallbackfunction for clarification between jsonpCallback and jsonCallbackFunction.