CODEWITHSUNDEEP
javascriptangularjsarraysscope
kashi viswanath
kashi viswanath

Reputation: 85

Why does array contain only last value n times?

This function returns the same value in the array list.

For example if i=10, then my array should contain 10 different values, but it stores only the last value 10 times.

What is the problem in my code? 

$scope.webTempIds=[];
$scope.wId={};
$scope.getIds=function(){
  for(var i=0;i<$rootScope.retData.length;i++){
    $scope.wId.ID=$rootScope.retData[i].WEBUI_TEMP_ID;
    $scope.webTempIds.push($scope.wId);
  }
  return $scope.webTempIds;
}

Upvotes: 3

Views: 100

Answers (4)

Matthew Cawley
Matthew Cawley

Reputation: 2818

As others have correctly pointed out, you end up with the last item in the array because the value that you push to the array is on the $scope and gets replaced with the new value each time.

To offer an alternative approach, you could use the Array.prototype.map function to return a new array prepopulated with just the id property values of each data item:

$scope.getIds=function(){
  $scope.webTempIds = $rootScope.retData.map(
    function(obj){ 
      return obj.id; 
    }
  );
}

This eliminates the need for any loops with temporary variables and any pushing to manually build up a new array from scratch.

Upvotes: 1

Maxim Shoustin
Maxim Shoustin

Reputation: 77904

This happens because you use $scope for wId.ID outside of loop. Therefore your list items point to the same object.

Once you change $scope.wId.ID , the list $scope.webTempIds will be updated too.

To fix it make id local:

for(var i=0;i<$rootScope.retData.length;i++){
     var wId = {
            ID: $rootScope.retData[i].WEBUI_TEMP_ID;
           }
     $scope.webTempIds.push(wId);
}

As a side note: use Scope to bind application controller and the view. (inside the for loop you don't need scope)

Upvotes: 3

mino
mino

Reputation: 36

    $scope.getIds=function(){
        $scope.webTempIds=[];
        for(var i=0;i<$rootScope.retData.length;i++){
            $scope.wId={};
            $scope.wId.ID  =$rootScope.retData[i].WEBUI_TEMP_ID;
            $scope.webTempIds.push($scope.wId);
        }
return $scope.webTempIds;
    }

Upvotes: 0

marvel308
marvel308

Reputation: 10458

$scope.wId={};

is changed every time. The array contains the reference to this object and hence when you change the value it changes the value in the array.

let obj = {};

let result = [];
for(let i = 0; i<10; i++){
    obj.a = i;
    result.push(obj);
}

console.log(result);

Upvotes: 3

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