Simple Hash Table implementation in JavaScript

Hash Tables.js

//Hash tables are collection of key value pairs.
//This hash function uses Array to store data and uses separate chaining to avoid key collusion.
//Only works on alphabetic character string keys.

class Hash {
  constructor(size = 5) {
    this.table = new Array(size);
  }
  //hashes the given key/value. Using the given key, it finds an index on the Table and returns that index.
  _hash(key) {
    let total = 0;
    let primeNum = 31;
    for (let i = 0; i < Math.min(key.length, 100); i++) {
      let char = key[i];
      let value = char.charCodeAt(0) - 96;
      total = (total * primeNum + value) % this.table.length;
    }
    return total;
  }

  //stores data in the table. Uses this._hash to get the index of the given key and pushes key - value pairs into that index. uses separate chaining to avoid key collusion.
  set(key, value) {
    let idx = this._hash(key);
    if (!this.table[idx]) this.table[idx] = [];
    this.table[idx].push([key, value]);
  }

  //Gets value of a given index.
  get(key) {
    let idx = this._hash(key);
    if (this.table[idx]) {
      for (let i = 0; i < this.table[idx].length; i++) {
        if (this.table[idx][i][0] === key) {
          return this.table[idx][i][1];
        }
      }
    }
    return undefined;
  }

  //returns all the keys that are in the table, also it avoids duplicates.
  keys() {
    let obj = {};
    this.table.map(data => {
      data &&
        data.map(d => {
          !obj[d[0]] ? (obj[d[0]] = d[0]) : null;
        });
    });
    return Object.keys(obj);
  }
  //returns all the values that are in the table.

  values() {
    const result = [];
    this.table.map(data => {
      data &&
        data.map(d => {
          result.push(d[1]);
        });
    });
    return result;
  }
}

//EXAMPLE
const HashFunction = new Hash();

HashFunction.set("name", "prottay");
HashFunction.set("age", 16);
HashFunction.set("have anxiety", "yes");
HashFunction.set("needs another laptop", "yes");
console.log(HashFunction.get("name"));
console.log(HashFunction.keys());
console.log(HashFunction.values());

export default HashFunction;