simple-int-hashmap.js

const MIN_BASE = 10;
const LIMIT = .7;
const GROW_SCALE = 2;

class HashMap
{
	constructor(base = MIN_BASE)
	{
		Object.assign(this, this._genNew(base));
	}

	_genNew(base)
	{
		return (
		{
			size: 0,
			_base: base,
			_storage: [...new Array(base)],
		});
	}

	_hash(key, base = this._base)
	{
		return key % base;
	}

	delete(key)
	{
		const idx = this._hash(key);
		let it = { next: this._storage[idx], root: true };

		while(it.next)
			if(it.next.key === key)
			{
				if(it.root)
				{
					this._storage[idx] = undefined;
					-- this.size;
					return;
				}

				it.next = it.next.next;
				-- this.size;
				return;
			}
			else it = it.next;
	}

	_isExceed()
	{
		return this.size >= LIMIT * this._base;
	}

	* entries()
	{
		for(const row of this._storage)
		{
			let el = row;
			while(el)
			{
				yield [el.key, el.val];
				el = el.next;
			}
		}
	}

	* [Symbol.iterator]()
	{
		for(const [, val] of this.entries())
			yield val;
	}

	* keys()
	{
		for(const [key] of this.entries())
			yield key;
	}

	_grow()
	{
		const newBase = this._base * GROW_SCALE;
		const hash = new HashMap(newBase);

		for(const [key, value] of this.entries())
			hash.set(key, value);

		this.size = hash.size;
		this._storage = hash._storage;
		this._base = hash._base;
	}

	set(key, val)
	{
		const exist = this._find(key);
		if(exist)
		{
			exist.val = val;
			return;
		}

		if(this._isExceed())
		{
			this._grow();
			this.set(key, val);
			return;
		}

		const idx = this._hash(key);
		const el =
			{
				key,
				val,
				next: null,
			};
		++ this.size;

		if(!this._storage[idx])
			this._storage[idx] = el;
		else
		{
			let last = this._storage[idx];
			while(last.next)
				last = last.next;

			last.next = el;
		}
	}

	_find(key)
	{
		const idx = this._hash(key);
		let it = { next: this._storage[idx] };

		while(it.next)
		{
			it = it.next;
			if(it.key === key)
				return it;
		}

		return null;
	}

	get(key)
	{
		const el = this._find(key);
		return el ? el.value : null;
	}

	has(key)
	{
		const el = this._find(key);
		return el !== null;
	}
};