'use strict';

const POOL_SIZE = 5;

const poolify = (factory) => {

const instances = new Array(POOL_SIZE).fill(null).map(factory);

const acquire = () => {

const instance = instances.pop() || factory();

console.log('Get from pool, count =', instances.length);

return instance;

};

const release = (instance) => {

instances.push(instance);

console.log('Recycle item, count =', instances.length);

};

return { acquire, release };

};

class Connection {

static index = 0;

constructor(url) {

this.url = url;

}

static create() {

return new Connection(`http://10.0.0.1/${Connection.index++}`);

}

}

// Usage

const pool = poolify(Connection.create);

for (let i = 0; i < 10; i++) {

const connection = pool.acquire();

console.log(connection);

}