Function compareN

docs/app/js/sanddance-app.js:106779–106789

(fields, orders, n)

        return ascending(field3(a), field3(b)) * order;
    };
const compareN = (fields, orders, n)=>{
    orders.push(0); // pad zero for convenient lookup
    return function(a, b) {
        let f, c = 0, i = -1;
        while(c === 0 && ++i < n){
            f = fields[i];
            c = ascending(f(a), f(b));
        }
        return c * orders[i];
    };
};
function constant(_) {
    return isFunction(_) ? _ : ()=>_;
}