num -> string -> array -> [sort(), reverse()] -> string -> num
JS is fun!
const descendingOrder = n => +[...''+n].sort().reverse().join``;
function descendingOrder(n){
return Number(String(n).split('').sort(function(a, b){return b-a}).join(''));
}
const descendingOrder = n =>
+[...''+n].sort().reverse().join``;