angular js adding two numbers issue

Question

angular js adding two numbers issue

I have this code using angular js:

<!DOCTYPE html >
<html>
<head>
    <title>Untitled Page</title>
    <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.5/angular.min.js"></script>
    <script type="text/javascript">
        function TodoCtrl($scope) {
            $scope.total = function () {
                return $scope.x + $scope.y;
            };

        }
    </script>
</head>
<body>
   <div ng-app>
  <h2>Calculate</h2>

  <div ng-controller="TodoCtrl">
    <form>
        <li>Number 1: <input type="text" ng-model="x" /> </li>
        <li>Number 2: <input type="text" ng-model="y" /> </li>
        <li>Total <input type="text" value="{{total()}}"/></li>       
    </form>
  </div>
</div>

</body>
</html>

I am able to do multiplication, division and subtraction but for addition, the code just concatenates the x and y values (i.e. if x = 3 and y = 4, the total is 34 instead of being 7)

What am I doing wrong?

javascript
angularjs

Answer 1

If that is indeed the case then what is happening is the values that are being passed in for x and y are being treated as strings and concatenated. What you should do is convert them to numbers using parseInt

return parseInt($scope.x) + parseInt($scope.y);

or if you prefer brevity

return $scope.x|0 + $scope.y|0;

Answer 2

You want this:

   return parseFloat($scope.x) + parseFloat($scope.y);

+ overrides string concatenation when you have 2 strings. You'll need to cast them to integers or floats explicitly. -,*,/ will all cast to numbers if possible.

Answer 3

To add two numbers together I would parse the string for Integers and check for null:

function TodoCtrl($scope) {
    $scope.total = function() {
        var firstNum = parseInt($scope.firstNum) 
        var secondNum = parseInt($scope.secondNum);

        if (!firstNum)
            firstNum = 0;
        if (!secondNum)
            secondNum = 0;

        return firstNum + secondNum;
    }
}

Answer 4

Adding floating numbers in correct way

 $scope.Total = parseFloat($scope.firstValue) + parseFloat($scope.secondValue);
 $scope.Total = parseFloat($scope.Total.toFixed(2));

The $scope.Total now will display correctly in the view if binding with ng-model is applied for example if you have

$scope.firstValue = 10.01;
$scope.firstValue = 0.7;

$scope.Total = parseFloat($scope.firstValue) + parseFloat($scope.secondValue);

The variable $scope.Total will be 10.709999999999999 and this is not correct! Adding with parseFloat will not be enough for a correct value. But if you apply

$scope.Total = parseFloat($scope.Total.toFixed(2));

The value will result correctly: $scope.Total = 10.71

Be careful will floating point numbers in javascript