delete(key) {
    const { bucket, entry } = this.getEntry(key);
    if (!entry) { return false; }

    return !!bucket.remove((node) => {
      if (key === node.value.key) {
        delete this.keysTrackerArray[node.value.order]; // O(1) deletion
        this.size -= 1;
        return true;
      }
      return undefined;
    });
  }
Removes the specified element from the map.
Avg. Runtime: O(1)
@param {*} key
@returns {boolean} true if an element in the map existed
 and has been removed, or false if the element did not exist.