在javascript

Question

我有一个以json格式获取数据的函数。为了在google maps api中显示标记，我创建了一个for循环来从json获取值并将它们设置在marker变量中。我尝试使用if语句只初始化Marker一次。

function setMarker() {
        $.getJSON('http://127.0.0.1:8000/locator/car/gpspos/', function(car_pos) {

            for (i = 0; i < car_pos["json_data_list"].length; i++){

                if (i==0){
                    marker [i] = new google.maps.Marker({
                        map: map,
                    });

                    userLat = car_pos["json_data_list"][i].latitude;
                    console.log(userLat);
                    userLon = car_pos["json_data_list"][i].longitude;
                    console.log(userLon);
                    var position = new google.maps.LatLng(userLat,userLon);
                    marker.setPosition(position);
                    map.setCenter(position);
                }

                else {

                    userLat = car_pos["json_data_list"][i].latitude;
                    console.log(userLat);
                    userLon = car_pos["json_data_list"][i].longitude;
                    console.log(userLon);
                    var position = new google.maps.LatLng(userLat,userLon);
                    marker.setPosition(position);
                    map.setCenter(position);
                }
            }

        });
    }

如果sombody可以帮助我使用for循环和if语句，我将不胜感激。

Answer 1

您不需要检查来初始化标记，您必须为JSON中的每个项目制作标记。

function setMarker() {
  $.getJSON('http://127.0.0.1:8000/locator/car/gpspos/', function(car_pos) {

    var marker = []; // don't forget the var keyword for local variables

    for (var i = 0; i < car_pos["json_data_list"].length; i++){ // same var keyword
        marker [i] = new google.maps.Marker({
          map: map
        });

        var userLat = car_pos["json_data_list"][i].latitude; // same var keyword
        console.log(userLat);
        var userLon = car_pos["json_data_list"][i].longitude; // same var keyword
        console.log(userLon);

        var position = new google.maps.LatLng(userLat,userLon);
        marker[i].setPosition(position); // marker[i] instead of marker
        map.setCenter(position); 
        // the map will be centered on the last marker added to the list.
    }
  });
}