simple implementation of Storage interface

MyStorage.js

export const MyStorage = (() => {
  const sym = Symbol();
  return class MyStorage {
    constructor() {
      if (arguments[0] !== sym) {
        return new Proxy(new MyStorage(sym), {
          get(target, prop) {
            if (prop === 'length') return target.length;
            const v = Reflect.get(target, prop);
            return typeof v === 'function' ? v.bind(target) : target.getItem(prop);
          },
          set(target, prop, value) {
            target.setItem(prop, value);
            return true;
          },
          deleteProperty(target, prop) {
            target.removeItem(prop);
            return true;
          },
        });
      }

      this.data = new Map();
    }
    key(n) {
      return [...this.data.keys()][n];
    }
    getItem(key) {
      return this.data.has(key) ? this.data.get(key) : null;
    }
    setItem(key, value) {
      this.data.set(key, value);
    }
    removeItem(key) {
      this.data.delete(key);
    }
    clear() {
      this.data.clear();
    }
    get length() {
      return [...this.data.keys()].length;
    }
  }
})();

export const myStorage = new MyStorage();