Implement a HashMap Algorithm

class HashMap {
  constructor(size = 53) {
    this.buckets = new Array(size);
    this.size = size;
  }

  _hash(key) {
    let hash = 0;
    const prime = 31;
    for (let i = 0; i < key.length; i++) {
      hash = (hash * prime + key.charCodeAt(i)) % this.size;
    }
    return hash;
  }

  set(key, value) {
    const index = this._hash(key);
    if (!this.buckets[index]) {
      this.buckets[index] = [];
    }

    const existing = this.buckets[index].find(([k]) => k === key);
    if (existing) {
      existing[1] = value;
    } else {
      this.buckets[index].push([key, value]);
    }
  }

  get(key) {
    const index = this._hash(key);
    const bucket = this.buckets[index];
    if (!bucket) return undefined;

    const pair = bucket.find(([k]) => k === key);
    return pair ? pair[1] : undefined;
  }

  delete(key) {
    const index = this._hash(key);
    const bucket = this.buckets[index];
    if (!bucket) return false;

    const i = bucket.findIndex(([k]) => k === key);
    if (i === -1) return false;

    bucket.splice(i, 1);
    return true;
  }

  keys() {
    const result = [];
    for (const bucket of this.buckets) {
      if (bucket) {
        for (const [key] of bucket) {
          result.push(key);
        }
      }
    }
    return result;
  }
}

const map = new HashMap();
map.set("name", "Ehsan");
map.set("role", "engineer");
map.set("lang", "TypeScript");

console.log(map.get("name"));  // "Ehsan"
console.log(map.get("role"));  // "engineer"
map.delete("lang");
console.log(map.keys());       // ["name", "role"]