Example of making an async React Native call to a .NET Web API 2 project.

rn-async-webapi.js

/*
 * Example of making an async React Native call to a .NET Web API 2 project.
 * Helped with this issue a few times now.. Note the content type.
 */

(async () => {
    // Make the API call
    fetch(constants.API_ROUTE+'Token', {
        method: 'POST',
        headers: {'Content-Type': 'application/x-www-form-urlencoded'},
        body: 'grant_type=password&username=USERNAME&password=PASSWORD'
    })
    .then(function(response) {
      // Do something cool
    })
    .catch(function(err) {
      // Tell the user something is broken
    });
})();