Second approach inspired by Stephen's answer @Stephen Lead
function style(feature) { var fa; return { color: getColor(feature.properties.paP), weight: fa * getWidth(feature.properties.stW), opacity: 0.6, lineCap: 'square', lineJoin: 'square', }; } map.on('zoomend', function () { var currentZoom = map.getZoom(); if (currentZoom <= 16) { fa = 0.5; } else { fa = 3; } });