比较数据库中的两个变量

Question

我正在尝试比较两个变量，但是我做错了什么，但我没有想要的结果。我在从$ scope到数组中输入数据时遇到问题。

我要补充一点，我是一个超级外行，我正在学习。

你可以看看这个吗？

继续主题：Difference between two adjacent numbers in array和Finding difference between consecutive numbers in an array in javascript

我的代码：

<div ng-app="myApp" ng-controller="customersCtrl">
  <div class="container">
    <div class="row">
      <div class="table">
        <table class="table" id="analyticsTable" ng-repeat="(key, value) in names | groupBy: 'view_id'">
          <thead>
            <tr>
              <td><strong>{{key}}</strong></td>
              <th ng-repeat="item in value | where:{year: 2017}">{{ item.month }}</th>
            </tr>
          </thead>
          <tr>
            <td>2017</td>
            <td ng-repeat="item in value | where:{year: 2017}">{{ item.visit }}</td>
          </tr>
          <tr>
            <td>2018</td>
            <td ng-repeat="item in value | where:{year: 2018}">{{ item.visit }}
              <span class="visited">{{ item.visit | myFormat }}</span>
            </td>
          </tr>
        </table>
      </div>
    </div>
  </div>
</div>

控制器代码：

app.controller('customersCtrl', function($scope, $http) {
  $http.get("ga_data.php")
    .then(function(response) {
      $scope.names = response.data.records;
    });
});

app.filter('myFormat', function() {
  return function(input, scope) {
    var number = "";

    checkVisitsDiff(x);

    function checkVisitsDiff(x) {
      if (!x || x.length < 2) {
        throw "Bad input!";
      }
      for (var i = 1; i < x.length; i++) {
        var currentElement = x[i];
        var previousElement = x[i - 1];
        number = (currentElement - previousElement);
      }
    }
    return number;
  }
});