OpenLayers按属性从GeoJSON创建图层 [英] OpenLayers create Layers from GeoJSON by property

问题描述

我想使用OpenLayers v5.3.0创建一个Web应用程序.

I want to use OpenLayers v5.3.0 to create a Web application.

我能够将外部GeoJSON文件中的所有功能显示为OSM层上方的矢量层，但是我的GeoJSON文件包含成千上万个功能，每个功能都具有许多特性.

I’m able to show all features from a external GeoJSON File as a Vector Layer above a OSM Layer, but my GeoJSON File holds thousands of features, each enriched by a lot of properties.

我正在查看的是一种能够解析GeoJSON文件，按属性(例如，具有属性"gender": "f",或"ethnic_gro": "Latvian",的所有特征)对其进行过滤并仅将其显示为上方的矢量层的方法我的OSM基本层.

What I’m looking at is a way to be able to parse the GeoJSON File, filter it by properties (e.g. all features with the property "gender": "f", or "ethnic_gro": "Latvian",) and display only those as an additional Vector Layer above my OSM Base Layer.

这是我的GeoJSON文件的一个示例(已附加，只有一个功能):

This is an example of my GeoJSON File (abbriviated, with only one Feature):

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "geometry": {
        "type": "LineString",
        "coordinates": [
          [23.114870000000053, 56.845980000000134],
          [19.131050000000164, 50.65641000000013]
        ]
      },
      "properties": {
        "OID_": "0",
        "ethnic_gro": "Latvian",
        "religion": "protestant",
        "marital_st": "widow",
        "status_in_": "NULL",
        "gender": "f",
      }
    }
  ]
}

感谢您的帮助！

推荐答案

您可以在原始要素数组上使用javascript数组过滤器来构建新的GeoJSON对象:

You could use a javascript array filter on the original features array to build a new GeoJSON object:

var filteredGeoJSON = {
  "type": "FeatureCollection",
  "features": fullGeoJSON.features.filter(function(feature){
     return (feature.properties.ethnic_gro == "Latvian" && feature.properties.gender == "f");
  })
};

或使用forEach循环来构建过滤后的数组:

or use a forEach loop to build a filtered array:

var filteredGeoJSON = { 
  "type": "FeatureCollection",
  "features": []
};
fullGeoJSON.features.forEach(function(feature){
  if (feature.properties.ethnic_gro == "Latvian" && feature.properties.gender == "f") {
    filteredGeoJSON.features.push(feature);
  }
});

这篇关于OpenLayers按属性从GeoJSON创建图层的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！