title: Array.prototype.find() returns undefined in async function
body: <p>I have an issue with the <code>Array.prototype.find()</code> method. It doesn't seem to work properly when it is used in <code>$http request..</code> I've tried everything that came to mind but it always returns undefined. I guess the bug is there because I logged <code>response.data</code> and <code>user_to_find</code> before defining <code>found_user</code> and their values are as expected.</p>
  
  <p><strong>So I have this service:</strong></p>
  
  <pre><code>app.service('UserService', ['$http','$q', function($http, $q) {
    return {
      findUser: function(user_to_find) {
        let defer = $q.defer();
        $http({
          method: "GET",
          url: 'http://localhost:3000/users'
        }).then(function(response){
          let found_user = response.data.find(acc=&gt;{ //found_user is always undefined
            acc.username == user_to_find;
          })
          defer.resolve(found_user);
        }),function(response) {
          defer.reject(response);
          console.log("Error finding user");
        }
        return defer.promise;
      }
    }
  }])
  </code></pre>