simple LRU using Map https://repl.it/@PatrickJS1/SpatialLegitimateProcedure#index.ts

map-lru.ts

class LRU extends Map {
 m = 10;
 get(k) {
  let i = super.get(k);
  if (i) {
    super.delete(k);
    super.set(k, i);
  }
  return i;
 }
 set(k, v) {
  super.delete(k);
  if (super.size == this.m) {
    super.delete(super.keys().next().value);
  }
  return super.set(k, v);
 }
}