javascript - 使用模块模式在传单 map 对象上运行方法

Question

我正在尝试封装我所有的 leaflet将函数映射到 module ，这样我就可以在应用程序的其他地方执行我的 map 函数。我的模块的所有函数都在私有(private)变量“map”上运行，即 leaflet map 对象。我遇到了条件语句的问题，该条件语句在将此图层添加到 map 之前检查 map 图层对象“neighborhood_polygon_layer”是否存在，以便在重新加载时不会复制该图层(如果该图层已存在)。 map 对象只是累积重复的图层对象，但map.hasLayer();函数从不检测条件语句中的这些对象。一旦这些对象被添加到 map 中，允许函数再次执行，变量“neighborhood_polygon_layer”就失去了对其对象的引用。

var sbk = sbk || {};

sbk.map = (function () {

    var map = L.mapbox.map('map', '[redacted map id]');

    return {

        render_neighborhood_polygons: function(polygonNeighborhoods, storyNeighborhoods, neighborhoods){
                var neighborhoodPolygons = [];
                var neighborhoodsIntersection = _.intersection(polygonNeighborhoods, storyNeighborhoods);
                neighborhoodsIntersection.forEach(function (neighborhood) {
                        neighborhoodPolygons.push(neighborhoods.get(neighborhood).attributes);
                });
                var neighborhood_polygon_layer = L.geoJson(neighborhoodPolygons);

            if(!map.hasLayer(neighborhood_polygon_layer)) {
                neighborhood_polygon_layer.addTo(map);
            }
    };
} ());

Answer 1

It's as if the variable "neighborhood_polygon_layer" looses it's reference to it's object once those objects are added to the map allowing the function to execute again.

否:

var neighborhood_polygon_layer = L.geoJson(neighborhoodPolygons);

这将创建一个名为 neighborhood_polygon_layer 的新图层，并通过 hasLayer 查看它是否位于 map 中。该图层永远不会出现在 map 中，因为您刚刚创建了它:图层并不===其中的数据。如果您只想运行此函数一次，可以在初始化时执行此操作，创建一个 bool 标志来确定它之前是否运行过，或者不要运行多次。