Function comparator

docs/app/js/sanddance-app.js:106775–106775

(fields, orders)

}
const ascending = (u, v)=>(u < v || u == null) && v != null ? -1 : (u > v || v == null) && u != null ? 1 : (v = v instanceof Date ? +v : v, u = u instanceof Date ? +u : u) !== u && v === v ? -1 : v !== v && u === u ? 1 : 0;
const comparator = (fields, orders)=>fields.length === 1 ? compare1(fields[0], orders[0]) : compareN(fields, orders, fields.length);
const compare1 = (field3, order)=>function(a, b) {
        return ascending(field3(a), field3(b)) * order;
    };