Mastering Web Application

Chapter 3

Dealing with HTTP responses

A request can either succeed or fail and AngularJS provides two methods to register
callbacks to deal with the two outcomes: success and error. Both the methods
accept a callback function that will be called with the following parameters:

• data: The actual response data


• status: The HTTP status of the response


• headers: A function giving access to the HTTP response headers


• config: The configuration object that was supplied when a request
  was triggered

AngularJS will invoke success callbacks for the HTTP responses with

status ranging from 200 to 299. Responses with a status outside of this

range will trigger the error callback. The redirection responses (HTTP

status 3xx codes) are automatically followed by a browser.

Both success and error callbacks are optional. If we don't register any callback a
response will be silently ignored.

Response data conversion

As with request data conversions, the $http service will try to convert responses
containing a JSON string into a JavaScript object. This conversion happens
before invoking success or error callbacks. The default conversion behavior
can be customized.

In the current version of AngularJS the $http service will try to

perform JSON string to JavaScript object conversion on any responses

that look like JSON (that is, starts with { or [ and end with ] or }).

Dealing with same-origin policy restrictions

Web browsers enforce the same-origin security policy. This policy authorizes XHR
interactions only with resources originating from the same source (defined as a
combination of a protocol, host and its port) and enforces restrictions on interactions
with "foreign" resources.