Angular $http json params transformReq no jQuery

var loginObj = {
  'username':   $scope.username,
  'password':   $scope.password,
  'grant_type': 'password',
  'client_id':  'web'
}

var doLogin = $http({
  method: 'POST',
  url: 'https://api/v1/token',
  headers: {'Content-Type': 'application/x-www-form-urlencoded'},
  transformRequest: function(obj) {
    var str = [];
    for(var p in obj) {
      str.push(encodeURIComponent(p) + '=' + encodeURIComponent(obj[p]));
    }
    return str.join('&');
  },
  data: loginObj,
  responseType: 'json'
})

doLogin.then(
  onLoginSuccess,
  onLoginError
)