class RoundRobinLB {
  constructor(servers) {
    this.servers = servers;
    this.index = 0;
  }

  next() {
    const server = this.servers[this.index % this.servers.length];
    this.index += 1;
    return server;
  }
}

class LeastConnectionsLB {
  constructor(servers) {
    this.servers = servers; // fixed order -- used to break ties deterministically
    this.connections = {};
    for (const s of servers) this.connections[s] = 0;
  }

  next() {
    let chosen = this.servers[0];
    for (const s of this.servers) {
      if (this.connections[s] < this.connections[chosen]) {
        chosen = s;
      }
    }
    this.connections[chosen] += 1;
    return chosen;
  }
}

const servers = ['A', 'B', 'C'];

const rr = new RoundRobinLB(servers);
const rrResult = [];
for (let i = 0; i < 7; i++) rrResult.push(rr.next());
console.log('Round robin:', rrResult);

const lc = new LeastConnectionsLB(servers);
const lcResult = [];
for (let i = 0; i < 5; i++) lcResult.push(lc.next());
console.log('Least connections:', lcResult);
console.log('Final connection counts:', lc.connections);