混淆的Javascript「然後」行爲

Question

我在角控制器下面的代碼...

function doWork() { 
    // show the loading modal 
    $scope.modal = $ionicLoading.show({ 
    content: 'Fetching current location...', 
    showBackdrop: false 
    }); 

    console.log("get orig pos"); 

    // get the position 
    PositionService.getPosition(posOptions) 
    .then(function(positionArr) { 
     // got 1st location // this doesn't execute! 
     console.log("got original pos: " + positionArr.length);   
     $scope.locationArray = positionArr; 
     $scope.dataReceived = true; 
     $scope.modal.hide(); 
    }, function(err) { 
     // something went wrong 
     console.log("something wrong in getPos"); 
     $timeout(function() { 
     $scope.modal.hide(); 
     }, 3000);   
    }); 

    console.log("get next pos"); 

    PositionService.getPosition(posOptions) 
    .then(function(positionArr) { 
     // got 2nd location // this does execute! 
     console.log("got new pos: " + positionArr.length);   
     $scope.locationArray = positionArr; 
     $scope.dataReceived = true; 
    }, function(err) { 
     // something went wrong 
     console.log("something wrong in getPos"); 
    }); 
} 

當我運行該程序的PositionService.getPosition函數被調用兩次，因爲我所期望的，但只有一個執行then部件。不應該兩個then塊被執行，或者我誤解這是如何工作在Javascript？這是getPosition功能的內容...

getPosition : function(posOptions) { 
     return $cordovaGeolocation 
     .getCurrentPosition(posOptions) 
     .then(function(position) { 
      positionArr = positionArr.concat({ 
      position: position, 
      status: 'new' 
      }); 
      return positionArr; 
     }, function(err) { 
      console.log("PositionService: error getting position"); 
      return err; 
     }); 
    }, 

編輯：

這裏的要求控制檯輸出...

Answer 1

你應該鏈你的位置服務電話：

var p1 = PositionService.getPosition(posOptions) 
    .then(function(positionArr) { 
     // got 1st location 
     console.log("got original pos: " + positionArr.length);   
     $scope.locationArray = positionArr; 
     $scope.dataReceived = true; 
     $scope.modal.hide(); 
    }, function(err) { 
     // something went wrong 
     console.log("something wrong in getPos"); 
     $timeout(function() { 
     $scope.modal.hide(); 
     }, 3000);   
    }); 

var p2 = p1.then (function() { 
    return PositionService.getPosition(posOptions); 
    }).then(function(positionArr) { 
     // got 2nd location 
     console.log("got new pos: " + positionArr.length);   
     $scope.locationArray = positionArr; 
     $scope.dataReceived = true; 
    }, function(err) { 
     // something went wrong 
     console.log("something wrong in getPos"); 
    }); 

Answer 2

第一。那麼（）回調一個'成功'，另一個是'錯誤'。所以這是其中的一個。防爆。 http請求可以是'200'或'404'（或其他錯誤）。

參見：http://blog.mediumequalsmessage.com/promise-deferred-objects-in-javascript-pt1-theory-and-semantics