Javascript sort

myJSsort.ts

a.sort((a, b) => {
  function convert(x: any) {
      return x[sortBy];
  }

  function compare() {
      const m = convert(a) || -Infinity;
      const n = convert(b) || -Infinity;
      if (typeof m === "string" && typeof n === "string") {
          return m.localeCompare(n);
      } else if (typeof m === "string") {
          return 1;
      } else if (typeof n === "string") {
          return -1;
      } else {
          return m - n;
      }
  }

  return desc ? -compare() : compare();
})