Function validate

docs/app/js/sanddance-app.js:103678–103681

(polygon)

    return arr2;
}
function validate(polygon) {
    polygon = polygon && polygon.positions || polygon;
    if (!Array.isArray(polygon) && !ArrayBuffer.isView(polygon)) throw new Error("invalid polygon");
}
function isSimple(polygon) {
    return polygon.length >= 1 && polygon[0].length >= 2 && Number.isFinite(polygon[0][0]);
}