When a vector layer is populated with features, it can be very useful to query the data source in order to retrieve feature information. OpenLayers provides some methods from the vector source class (
ol.source.Vector) that enable us to perform queries, such as finding out what features are within a custom extent (
getFeaturesInExtent), or returning any features at a particular coordinate (
getFeaturesAtCoordinate), as well as other useful types of queries.
We are going to create a map with a tile raster layer and a vector layer with features from a custom GeoJSON file. The polygon features will represent campsites within a region, each with some properties that can be extracted for display. We will call the
getFeaturesAtCoordinate source query method when the map is clicked on and display the applicable feature information within
overlay if a feature exists at this coordinate.
The source code can be found in