🗂️ Custom HashMap Implementation in TypeScript

This project provides a custom HashMap<K, V> class implemented in TypeScript.
It mimics the behavior of JavaScript’s built-in Map but with an internal hashing mechanism and bucket-based collision handling.

🚀 Features

• Supports all primitive types (string, number, boolean, bigint, symbol, null, undefined) as keys.
• Supports object and function keys via unique object IDs.
• Automatic resize when load factor exceeds the threshold.
• Provides common map operations:
  • set(key, value)
  • get(key)
  • has(key)
  • delete(key)
  • clear()
  • Iterators: entries(), keys(), values()
  • forEach(callback)
• Fully typed with TypeScript generics (HashMap<K, V>).
• Implements [Symbol.iterator] for direct iteration.

📦 Installation

Clone the repository and install dependencies:

git clone https://github.com/SadjadSadeghi/real-hashmap.git
cd real-hashmap
npm install

Build: npm run build

Usage:

import { HashMap } from "real-hashmap";

const map = new HashMap<string, number>();

map.set("apple", 1);
map.set("banana", 2);

console.log(map.get("apple")); // 1
console.log(map.has("banana")); // true
console.log(map.size); // 2

map.delete("banana");
console.log(map.has("banana")); // false

// Iterate
for (const [key, value] of map) {
  console.log(key, value);
}

How Keys Work

Strings: Hashed using a polynomial rolling hash.

Numbers / Booleans / BigInts: Stringified with a prefix.

Symbols: Converted to string with unique prefix.

Objects & Functions: Assigned a unique object ID using WeakMap

Example:

const obj = {};
map.set(obj, "hello");

console.log(map.get(obj)); // "hello"

Configuration

You can control:

initialCapacity (default: 16)

loadFactor (default: 0.75)

const customMap = new HashMap<number, string>(32, 0.5);

Testing

We use Jest for unit testing.

Install types if missing:

npm i --save-dev jest @types/jest ts-jest


Run tests:
npm test