A naive JS implementation of hashtable using Linear Probing to solve collisions

hashtable.js

let HashTable = function() {
	let entries = [];

	this.put = (key, value) => {
		let hashKey = hashCode(key);
		let entry = entries[hashKey];
		
		// Linear Probing
		while (entry) {
			if (entry && entry[0] === key) break;

			hashKey++;
			entry = entries[hashKey];
		}

		entries[hashKey] = [key, value];
	};

	this.get = (key) => {
		let hashKey = hashCode(key);
		let entry = null;

		// Linear Probing
		while (!entry && hashKey < entries.length) {
			entry = entries[hashKey];
			if (entry && entry[0] === key) return entry[1];

			entry = null;
			hashKey++;
		}

		return null;
	};

	this.delete = (key) => {
		let hashKey = hashCode(key);
		let entry = null;

		// Linear Probing
		while (!entry && hashKey < entries.length) {
			entry = entries[hashKey];
			if (entry && entry[0] === key) entries[hashKey] = null;

			entry = null;
			hashKey++;
		}
	};

	this.keys = () => {
		let entryKeys = [];

		for (let i = 0; i < entries.length; i++) {
			if (entries[i]) entryKeys.push(entries[i][0]);
		}

		return entryKeys;
	};

	this.size = () => {
		var count = 0;

		for (let i = 0; i < entries.length; i++) {
			if (entries[i]) count++;
		}

		return count;
	};

	let hashCode = (s) => {
		let hash = 0;

		for (let i = 0; i < s.length; i++) {
	     	hash = s.charCodeAt(i++) | 0;
		}

		let value = Math.round(hash / 2);
		if (value === -0) value = 0;
		else if (value < 0) value *= -1;

		return value;
	}
};

let test = function () {
	let contacts = new HashTable();
	contacts.put("Batman", "bat@man.com");
	contacts.put("Superman", "super@man.com");
	contacts.put("Spiderman", "spider@man.com");

	console.log(`1st test >> There has only ${contacts.size()} sups`);
	console.log(`Batman <${contacts.get("Batman")}>`);
	console.log(`Superman <${contacts.get("Superman")}>`);
	console.log(`Spiderman <${contacts.get("Spiderman")}>`);
	console.log(`Acquaman <${contacts.get("Acquaman")}>`);

	contacts.put("Acquaman", "acqua@man.com");

	console.log(`\n2nd test >> There has ${contacts.size()} sups now`);
	console.log(`Batman <${contacts.get("Batman")}>`);
	console.log(`Superman <${contacts.get("Superman")}>`);
	console.log(`Spiderman <${contacts.get("Spiderman")}>`);
	console.log(`Acquaman <${contacts.get("Acquaman")}>`);

	contacts.delete("Superman");

	console.log(`\n3rd test >> Now we have only ${contacts.size()} again`);
	console.log(`Batman <${contacts.get("Batman")}>`);
	console.log(`Superman <${contacts.get("Superman")}>`);
	console.log(`Spiderman <${contacts.get("Spiderman")}>`);
	console.log(`Acquaman <${contacts.get("Acquaman")}>`);

	contacts.put("Batman", "bat@mail.com");

	console.log(`\n4nd test >> And then Bat chaged this email address 'cause Batman`);
	console.log(`Batman <${contacts.get("Batman")}>`);
	console.log(`Superman <${contacts.get("Superman")}>`);
	console.log(`Spiderman <${contacts.get("Spiderman")}>`);
	console.log(`Acquaman <${contacts.get("Acquaman")}>`);
}

test();

A sample output should look like this:

$ node hashtable.js
1st test >> There has only 3 sups
Batman <bat@man.com>
Superman <super@man.com>
Spiderman <spider@man.com>
Acquaman <null>

2nd test >> There has 4 sups now
Batman <bat@man.com>
Superman <super@man.com>
Spiderman <spider@man.com>
Acquaman <acqua@man.com>

3rd test >> Now we have only 3 again
Batman <bat@man.com>
Superman <null>
Spiderman <spider@man.com>
Acquaman <acqua@man.com>

4nd test >> And then Bat chaged this email address 'cause Batman
Batman <bat@mail.com>
Superman <null>
Spiderman <spider@man.com>
Acquaman <acqua@man.com>

And btw this is meant for education purpose only. You shouldn't try it in prodution (LOL).