What is ol?
The 'ol' npm package, also known as OpenLayers, is a powerful library for displaying map data in web browsers. It provides a comprehensive set of tools for working with maps, including support for various map layers, projections, and interactions. OpenLayers is highly customizable and can be used to create complex mapping applications.
What are ol's main functionalities?
Creating a Map
This code initializes a basic map using OpenStreetMap (OSM) as the tile source. The map is centered at a specific longitude and latitude and is set to a zoom level of 4.
const map = new ol.Map({
target: 'map',
layers: [
new ol.layer.Tile({
source: new ol.source.OSM()
})
],
view: new ol.View({
center: ol.proj.fromLonLat([37.41, 8.82]),
zoom: 4
})
});
Adding Vector Layers
This code adds a vector layer to the map. The vector layer contains a single point feature, which is placed at a specific longitude and latitude.
const vectorLayer = new ol.layer.Vector({
source: new ol.source.Vector({
features: [
new ol.Feature({
geometry: new ol.geom.Point(ol.proj.fromLonLat([37.41, 8.82]))
})
]
})
});
map.addLayer(vectorLayer);
Handling Map Interactions
This code adds a select interaction to the map, allowing users to click on features. When a feature is selected, the selected features are logged to the console.
const select = new ol.interaction.Select();
map.addInteraction(select);
select.on('select', function(e) {
console.log('Selected features:', e.selected);
});
Other packages similar to ol
leaflet
Leaflet is a popular open-source JavaScript library for mobile-friendly interactive maps. It is lightweight and easy to use, making it a good choice for simple mapping applications. Compared to OpenLayers, Leaflet has a smaller feature set but is often preferred for its simplicity and ease of use.
mapbox-gl
Mapbox GL JS is a powerful library for rendering interactive maps using WebGL. It offers high performance and a wide range of features, including support for custom vector tiles and 3D terrain. Compared to OpenLayers, Mapbox GL JS provides more advanced rendering capabilities but may require a Mapbox account for certain features.
cesium
Cesium is a JavaScript library for creating 3D globes and maps. It is designed for high-performance visualization of large datasets and supports a wide range of data formats. Compared to OpenLayers, Cesium is more focused on 3D visualization and is often used for applications that require a 3D perspective.
ol
OpenLayers as ES2015 modules.
Usage
Add the ol
package as a dependency to your project.
npm install ol --save
Import just what you need for your application:
import Map from 'ol/map';
import View from 'ol/view';
import TileLayer from 'ol/layer/tile';
import XYZ from 'ol/source/xyz';
new Map({
target: 'map',
layers: [
new TileLayer({
source: new XYZ({
url: 'https://{a-c}.tile.openstreetmap.org/{z}/{x}/{y}.png'
})
})
],
view: new View({
center: [0, 0],
zoom: 2
})
});
See the following examples for more detail on bundling OpenLayers with your application:
Module Identifiers
The module identifiers above (e.g. ol/map
) are like the ol.Map
names in the API documentation with /
instead of .
and all lowercase. Each module only has a default
export (there are no other named exports).
Constructors are exported from dedicated modules. For example, the ol/layer/tile
module exports the Tile
layer constructor.
Utility functions are available as properties of the default export from utility modules. For example, the getCenter
function is a property of the default export from the ol/extent
utility module.
Caveats
- The WebGL renderer is not available in this package.