length array in OpenLayers.Layer.Vector

Question

how to find length array (markers) in OpenLayers.Layer.Vector ?

var data = new OpenLayers.Layer.Vector("Data", {
    styleMap: styleMap,
    strategies: [new OpenLayers.Strategy.Fixed()],
    protocol: new OpenLayers.Protocol.HTTP({
        url: "./data/data.geojson",
        format: new OpenLayers.Format.GeoJSON({
            extractStyles: true, 
            extractAttributes: true,
            maxDepth: 2
        })
    })
}); 

Answer 1

data.events.register("loadend", data, function() { console.log(data.features.length); });