Error during minify.sh

Hi Anton, help me with this please:
I have this piece of code, which is correct:

contextmenu.on('open', function (evt) {
var feature = mapa.forEachFeatureAtPixel(evt.pixel, ft => ft);
            if (feature && feature.get('type') === 'removable') {
                contextmenu.clear();
                removeMarkerItem.data = { marker: feature };
                contextmenu.push(removeMarkerItem);
            } else {
                contextmenu.clear();
                contextmenu.extend(contextmenu_items);
                contextmenu.extend(contextmenu.getDefaultItems());
           }
        });

When I execute minify.sh, it throws this error:

[ERR] C2000: Rhino Parse Error (syntax error => var feature = mapa.forEachFeatureAtPixel(evt.pixel, ft => ft);) -- /Users/xxxxxx/IntelliJ IDEA/traccar/traccar-web/web/app/view/map/BaseMap.js:425:70
[ERR] C2000: Rhino Parse Error (Compilation produced 1 syntax errors. => null) -- /Users/xxxxxx/IntelliJ IDEA/traccar/traccar-web/web/app/view/map/BaseMap.js:1
[ERR] Compilation produced 1 syntax errors.

The code runs OK, the problem is that I can't minify the file.
What's that warning and how can I fix it?
The exactly place of the error is this: ft => ft

Thank you very much!!

My guess would be that you are trying to use features from ES6, which is probably not supported.

Hi, the problem was about "arrow functions".
The fix is:
Before:

var feature = mapa.forEachFeatureAtPixel(evt.pixel, ft => ft);

After:

var feature = mapa.forEachFeatureAtPixel(evt.pixel, function(feature, layer) { return feature; });

Best Regards