Q:

Paypal API with angular and cURL

Currently I'm working with paypal API and flowing with this document make your first call.  
When I sent a request through angular $http to paypal, I got a Status Code 415. It's seems like I missed something, does anyone can help me? :)
here is my code
 $http({
        url: 'https://api.sandbox.paypal.com/v1/oauth2/token',
        method: 'POST',
        headers: {'Content-Type': 'application/json', 
                  'auth-token': 'EOJ2S-Z6OoN_le_KS1d75wsZ6y0SFdVsY9183IvxFyZp EClusMEUk8e9ihI7ZdVLF5cZ6y0SFdVsY9183IvxFyZp',
                  'Accept-Language': 'en_US'
                  },
        data: { 'grant_type': 'client_credentials' }
}).success(function (data, status, headers, config) {
            console.log(data)
}).error(function (data, status, headers, config) {
            console.log(data)
});

A:

Referring to the Paypal doc

Tip: If you're using Windows, we recommend you make cURL calls using a
  Bash shell. If you're not using cURL calls, set the content-type to
  application/x-www-form-urlencoded for this request.

Try set the content_type as application/x-www-form-urlencoded

