OpenLayers: can't i get features of VectorSource outside of event listener?

Question

i'm trying to show only a certain feature from my Vector Source. so i make a function like this:

function showUtility(id) {
        utilitiesSource.forEach(function(i) {
            //console.log(i.getFeatures());
            i.forEachFeature(function(f) {
                if (f.getProperties().id == id) {
                    f.setStyle(null);
                } else {
                    f.setStyle([]);
                }
            });
        });
}

where the utilitiesSource comes from:

utilitiesSource = [];

var utilitySource = new ol.source.Vector({
                format: new ol.format.GeoJSON(),
                projection: 'EPSG:4326',
                url: 'someUrl',
                extractStyles: false
        });

utilitiesSource.push(utilitySource);

the problem is console.log(i.getFeatures()) in showUtility() always gives empty array although it's fine if i was using it in an eventlistener like these:

    var selectCtrl = new ol.control.Select({
        source: utilitiesSource,
        property: $(".options select").val(),
        selectLabel: 'Cari',
        addLabel: 'Tambah Kondisi',
        allLabel: 'Cocokkan Semua',
        attrPlaceHolder: 'atribut',
        valuePlaceHolder: 'nilai'
    });

 selectCtrl.on('select', function(e) {
        select.getFeatures().clear();
        utilitiesSource.forEach(function(i) {
            //console.log(i.getFeatures()); --> gives array of feature
            i.forEachFeature(function(f) {
                f.setStyle([]);
            });
        })
        e.features.forEach(function(f) {
            f.setStyle(null);
        });
    });

    var bar = new ol.control.Bar({ 
      group: true,
      controls: [
        selectCtrl,
        new ol.control.Button({
          html: '<i class="fa fa-undo" ></i>',
          title: 'Reset',
          handleClick: function() {
            select.getFeatures().clear();
            utilitiesSource.forEach(function(i) {
                //console.log(i.getFeatures()); --> gives array of feature
                i.getFeatures().forEach(function(f) {
                    f.setStyle(null);
                });
            })
          }
        })
     ]});

and if i use browser's console and execute utilitiesSource.forEach(function(i) { i.getFeatures().forEach(function(j){ if (j.getProperties().id == 100) {j.setStyle(null);} else {j.setStyle([])} });}); i get what i want

why is that? why can't i get the features in showUtility(id)?

Answer 1

(still not enough reputation so i have to ask questions awkwardly in the comments -.-)

have you tried calling your function after a setTimeout()? The geojson source loads the data asynchronously, so even calling it at the last line of code might be too early. I think this should still be up-to-date.