无法将对象推入数组，javascript

Question

我不明白为什么下面的行失败。

locations.push(location); 

我想创建充满位置对象（注释，经度，纬度）的阵列（位置）。注释也是一个数组，但充满了注释对象（ID，智能区，时间戳，条目，操作）。

以下是代码片段。

var map;  
var locations = []; 

function Location() { 
    this.annotations = []; /* Array of annotations */ 
    this.latitude = null; /* Location latitude */ 
    this.longitude = null; /* Location longitude */ 
} 

function Annotation() { 
    this.ID  = null; 
    this.smartzone = null; 
    this.timestamp = null; 
    this.entry  = null; 
    this.action = null; 
} 

function initialize() { 
    var mapOptions = { 
     center: new google.maps.LatLng(42.73, -84.49), 
     zoom: 15, 
     mapTypeId: google.maps.MapTypeId.ROADMAP 
    }; 

    map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions); 

    $.getJSON("http://www.site.com/pathto/map/json.php", function(data) { 
     $.each(data, function(key, val) { 

      //alert(val.ID); 
      var location = new Location(); 
      var annotation = new Annotation(); 

      if (locations.length === 0) { 

       annotation.ID  = val.ID; 
       annotation.smartzone = val.smartzone; 
       annotation.timestamp = val.timestamp; 
       annotation.entry  = val.entry; 
       annotation.action = val.action; 

       location.annotations.push(annotation); 

       location.latitide = val.latitude; 
       location.longitude = val.longitude; 

       locations.push(location); /* This is the line that fails */ 

      } else { 

       var locationExists = false; 

       for (var i = 0; i < annotations.length; i++) { 

        if (val.latitude == locations[i].latitude && val.longitude == locations[i].longitude) { 

         locationExists = true; 
        } 
       } 

       if (locationExists) { 

        annotation.ID  = val.ID; 
        annotation.smartzone = val.smartzone; 
        annotation.timestamp = val.timestamp; 
        annotation.entry  = val.entry; 
        annotation.action = val.action; 

        locations[i].annotations.push(annotation); 

       } else { 

        annotation.ID  = val.ID; 
        annotation.smartzone = val.smartzone; 
        annotation.timestamp = val.timestamp; 
        annotation.entry  = val.entry; 
        annotation.action = val.action; 

        location.annotations.push(annotation); 

        location.latitide = val.latitude; 
        location.longitude = val.longitude; 
        //locations.push(location); /* Same problem */ 
       } 
      }   
     }); 
    }); 
} 

Answer 1

我不知道这是正确的：

for (var i = 0; i < annotations.length; i++) { 

annotations不被任何定义。所以这个循环不应该执行。

这意味着i将永远是0当你在这里：

locations[i].annotations.push(annotation) 

其中老实说，我不知道为什么你的i计数器反正这样做，即使工作，似乎没有与locations阵列中的索引有任何关系。我认为你需要一些计数器来增加每次执行$.each()循环。

最后，而在其他情况下，您尝试使用计数器（即locations[i]）以指示要添加的数组中的项目似乎奇怪的是，在某些情况下，你想将数据添加到locations使用push()。我认为你需要在这里保持一致。

对我来说，在循环逻辑流程可以更好地被这样做：

// have a means to store location hash with value for index location in locations 
// this prevents you from having to iterate over locations array for each data element to see if location already exists 
// this would be defined at the beginning along with locations 
var locationMap = {}; 


// this would take place inside your getJSON success function 
// counter for incrementing location index 
var locationCount = 0; 
$.each(...) { // iterate the data 
    // create simple hash of lat/long 
    var locationHash = val.latitude + val.longitude; 
    // determine if location already exists 
    if(locationMap[locationHash] == undefined) { // this is new location 
     var location = new Location(); 
     var location.annotations[0] = new Annotation(); 

     // not shown - populate location and annotation property values 

     // add to locations array 
     locations[locationCount] = location; 

     // add hash to location map 
     locationMap[locationHash] = locationCount; 

     // increment location counter 
     locationCount++; 
    } else { 
     var locationIndex = locationMap[locationHash]; 
     var annotation = new Annotation; 

     // not shown - populate annotation property values 

     // add new annotation to existing location 
     location[locationIndex].annotations.push(annotation); 
    } 
}