fetch(url: String) : Promise<ResponseObject>
Returns a promise for the result of the call. A
then() clause attached to this takes a single argument; that argument is a callback function which takes a single argument, which is the result of the call. The result of the call is an object with two elements: A status property indicating the HTTP response status of the call, and
json() function, which returns a promise for the dictionary containing the body of the response (which is expected to be JSON).