In Javascript, create a hash table from scratch without using Map or Set.

hashmapFunctional.js

function createHashTable(size = 53) {
  // Initialize an array of given size to store key-value pairs (buckets)
  const buckets = new Array(size);

  // Hash function to convert a key into an index
  function hash(key) {
    let hash = 0;
    for (let i = 0; i < key.length; i++) {
      hash = (hash + key.charCodeAt(i) * 23) % size;
    }
    return hash;
  }

  // Insert or update a key-value pair in the hash table
  function set(key, value) {
    const index = hash(key);

    // If no bucket exists at this index, create an empty array
    if (!buckets[index]) {
      buckets[index] = [];
    }

    // Check if key already exists and update its value
    for (let pair of buckets[index]) {
      if (pair[0] === key) {
        pair[1] = value; // Update existing key with new value
        return;
      }
    }

    // If key does not exist, add a new key-value pair
    buckets[index].push([key, value]);
  }

  // Retrieve a value by its key
  function get(key) {
    const index = hash(key);

    // If no bucket exists at this index, return undefined
    if (!buckets[index]) return undefined;

    // Search for the key in the bucket and return its value if found
    for (let pair of buckets[index]) {
      if (pair[0] === key) return pair[1];
    }

    return undefined; // Return undefined if key is not found
  }

  // Delete a key-value pair from the hash table
  function remove(key) {
    const index = hash(key);

    // If no bucket exists at this index, return false (key not found)
    if (!buckets[index]) return false;

    // Iterate through the bucket and remove the key-value pair if found
    for (let i = 0; i < buckets[index].length; i++) {
      if (buckets[index][i][0] === key) {
        buckets[index].splice(i, 1);
        return true; // Key was successfully deleted
      }
    }

    return false; // Return false if key was not found
  }

  // Return an array of all keys in the hash table
  function keys() {
    const keysArray = [];

    // Iterate through all buckets and collect keys
    for (let bucket of buckets) {
      if (bucket) {
        for (let pair of bucket) {
          keysArray.push(pair[0]);
        }
      }
    }

    return keysArray;
  }

  // Return an array of all values in the hash table
  function values() {
    const valuesArray = [];

    // Iterate through all buckets and collect values
    for (let bucket of buckets) {
      if (bucket) {
        for (let pair of bucket) {
          valuesArray.push(pair[1]);
        }
      }
    }

    return valuesArray;
  }

  // Return an object exposing hash table operations
  return { set, get, remove, keys, values };
}

// Example usage:
const ht = createHashTable();
ht.set("name", "Alice");
ht.set("age", 25);
ht.set("occupation", "Engineer");

console.log(ht.get("name")); // Alice
console.log(ht.get("age")); // 25
console.log(ht.remove("age")); // true
console.log(ht.get("age")); // undefined
console.log(ht.keys()); // ["name", "occupation"]
console.log(ht.values()); // ["Alice", "Engineer"]

This approach avoids using class and leverages function closures to encapsulate the hash table behavior.