Question

在角度中获取 JSON 的长度

2017-10-28

3539

javascript angularjs json

{ "questions": [
  {
   "text": "Which colors do you see in the rainbow?",
   "answer": "A",
   "A": "RED",
   "B": "ORANGE",
   "C": "YELLOW",
   "D": "GREEN"
 },
 {
  "text": "What is sanatbek's family name?",
  "answer": "C",
  "A": "Saidov",
  "B": "Muhammadlatipov",
  "C": "Matlatipov",
  "D": "Boboyev"
 },
 {
  "text": "How many members does this company have?",
  "answer": "C",
  "A": "3",
  "B": "8",
  "C": "9",
  "D": "2"
 }
 ]
}

这是我的 JSON 文件，我需要在 AngularJS 中获取问题的长度，如下所示：

function getQuestionCount() {
    return $scope.questions.length;
}

此处 $scope.questions 在控制器中声明：我尝试过多种解决方案，例如

return Object.keys($scope.questions).length 这是 returning value: 6 ; 在显示 console.log($scope.questions) 之后。我明白这是我解析对象的属性数量。
然后经过一番思考，我尝试了这个 return $scope.questions.data.questions.length; 这是可行的。但是，我的控制台上显示以下错误。

这是我的错误消息：

错误消息

TypeError: Cannot read property 'data' of undefined.

Answer 1

从您分享的屏幕截图可以看出，您进行了 HTTP GET 调用来检索数据。调用成功完成后，您可以在范围内的变量中设置问题长度。

$http({
  method: 'GET',
  url: '/someUrl'
}).then(function successCallback(response) {
    $scope.questionsLenght = response.data.questions.length;
  }, function errorCallback(response) {
    // called asynchronously if an error occurs
    // or server returns response with an error status.
  });

Answer 2

如果在您的控制器中将 json 字符串设置为

  $scope.questions = {
  "questions": [
  {
      "text": "Which colors do you see in the rainbow?",
      "answer": "A",
      "A": "RED",
      "B": "ORANGE",
      "C": "YELLOW",
      "D": "GREEN"
  },
 {
     "text": "What is sanatbek's family name?",
     "answer": "C",
     "A": "Saidov",
     "B": "Muhammadlatipov",
     "C": "Matlatipov",
     "D": "Boboyev"
 },
 {
     "text": "How many members does this company have?",
     "answer": "C",
     "A": "3",
     "B": "8",
     "C": "9",
     "D": "2"
 }
    ]
};

尝试

 $scope.questions.questions.length;

因为您的 json 字符串中的数组名称是问题

Answer 3

您可以使用 for 循环获取长度：

for (var i = 0; i < $scope.questions.length; i++) {
   $scope.data.push(angular.copy(types[i]));
  }