javascript - javascript中通过动态变量访问对象

Question

我想访问动态变量中的对象

$scope.positionindifferentplaces = [ {
    "DeviceName" : "Device 1",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 12.9716,
    "Longitude" : 77.5946,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 2",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 17.3850,
    "Longitude" : 78.4867,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 3",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 21.2514,
    "Longitude" : 81.6296,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 4",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 28.7041,
    "Longitude" : 77.1025,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}]

我只想通过该值访问纬度和经度所需的变量是这样的

    var directionCoordinates = [ {
        lat : 12.9716,
        lng : 77.5946
    }, {
        lat : 17.3850,
        lng : 78.4867
    }, {
        lat : 21.2514,
        lng : 81.6296
    }, {
        lat : 28.7041,
        lng : 77.1025
    } ];

我想让这个变量动态化，我已经尝试过这样的事情

 for (var i = 0; i < positionindifferentplaces .length; ++i) { 
          var directionCoordinates = {
        lat :$scope.positionindifferentplaces [i].Latitude,
        lng :$scope.positionindifferentplaces [i].Longitude }; }

但它不起作用，请帮我解决这个问题

Answer 1

有两件事:

1)您在 for 循环中缺少使用positionotherplaces 而不是 $scope.positionotherplaces。

2) 您正在每个 for 循环中重新初始化方向坐标。相反，您应该在 for 循环之外将 DirectionCoordinates 定义为数组，然后在 for 循环中将对象插入其中

完整代码如下:

  $scope.positionindifferentplaces = [ {
    "DeviceName" : "Device 1",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 12.9716,
    "Longitude" : 77.5946,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 2",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 17.3850,
    "Longitude" : 78.4867,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 3",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 21.2514,
    "Longitude" : 81.6296,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}, {
    "DeviceName" : "Device 4",
    "DeviceID" : "10000005",
    "Date" : "2017-09-22T03:35:38-05:00",
    "Latitude" : 28.7041,
    "Longitude" : 77.1025,
    "Type" : "GPS",
    "Speed(mph)" : 64,
    "Speed(km/h)" : 103,
    "Altitude(ft)" : 68,
    "Altitude(m)" : 21,
    "Accuracy" : 5
}];

var directionCoordinates = [];
for (var i = 0; i < $scope.positionindifferentplaces .length; ++i) { 
          directionCoordinates.push({
             lat :$scope.positionindifferentplaces [i].Latitude,
             lng :$scope.positionindifferentplaces [i].Longitude
          }; 

}