javascript - 无法在angularJS中进行数学计算

我想要达到的目标就是这样。将有两栏，一栏是我当前持有的产品数量，另一栏是包装栏，它将有一个默认值为0的文本框，当我在该文本框内更改值并按提交按钮时，我想要该值从我的第一列（数量）中减去（完成）。在此之后，我想在最后一列中将文本框中的值加起来并继续操作，以便我可以看到到目前为止包装了多少物品
到目前为止，我已经做了这样的事情

<div ng-app='myApp' ng-controller="MainCtrl">
<div ng-repeat="prdElement in packageElement track by $index" class="package-grid">
    <table class="hovertable">
        <thead>
            <tr>
                <th>Line #</th>
                <th>Quantity in Plt</th>
                <th>Allready Packed</th>
            </tr>
        </thead>
        <tbody>
            <tr ng-repeat="data in prdElement.Data" ng-init="data.newquantity  = 0">
                <td>{{data.itemId}}</td>
                <td>
                    <input type="text" ng-model="data.newquantity" placeholder="Quantity" required=required />
                </td>
                <td>{{data.packed}}</td>
            </tr>
            <tr>
                <td width="100%" colspan="4">
                    <button ng-show="prdElement.show" ng-click="newPackageItem( prdElement,$event)">Next Pallet</button>
                </td>
            </tr>
        </tbody>
    </table>
</div>

    (function () {
    angular.module('myApp', []).controller('MainCtrl', function ($scope) {
        var counter = 0;
        $scope.packageElement = [{
            name: counter,
            show: true,
            Data: [{
                name: 'item 1',
                itemId: '284307',
                quantity: '100',
                packed: 0

            }, {
                name: 'item 2',
                itemId: '284308',
                quantity: '200',
                packed: 0
            }]
        }];

        $scope.newPackageItem = function (packageElement, $event) {

            var npackageElement = {};
            angular.copy(packageElement, npackageElement);
            counter++;
            packageElement.show = false;

            npackageElement.name = counter;
            angular.forEach(npackageElement.Data, function (row) {
                if (row.quantity != row.newquantity || row.quantity != 0) {
                    row.quantity = row.quantity - row.newquantity;
                    row.packed = row.newquantity;
                }

            });

            npackageElement.show = true;
            angular.forEach(packageElement.Data, function (row) {
                row.packed = row.packed + row.newquantity;
            });
            $scope.packageElement.push(npackageElement);

        };
    });

}());

除了添加Quantity in Plt并按下按钮外，所有操作都已完成，我希望将该数量显示在最后一列（已打包）中，并在后续行中进行跟踪。如您所见，我已经尝试过

 row.packed = row.packed + row.newquantity;

但是加法操作不正确，而是值连接在一起。
Fiddle

最佳答案

尝试

row.packed = Number(row.packed) + Number(row.newquantity);

这是fiddle