Before getting started

As we will mainly focus on attribute management in this chapter, we will need a vector layer with lots of attributes. I have prepared such a layer to work with. It can be located in the res folder of the code annex, and its name is world_countries.geojson. Before we make some progress, let's change our default vector layer from the capitals of the world to this one:

var map = new ol.Map({
    […]
        new ol.layer.Vector({
            source: new ol.source.Vector({
                format: new ol.format.GeoJSON({
                    defaultDataProjection: 'EPSG:4326'
                }),
                url: '../../res/world_countries.geojson',
            }),
            name: 'World Countries'
        })
    ],
    […]
});