Easily perform Concurrent Execution to LongRunning Processes using Simple ConcurrentQueue. Feel free to improve and share feedback.

concurrentProcessExecutor.js

const delay = (seconds = 1) =>
  new Promise((resolve, reject) =>
    setTimeout(() => {
      resolve("process completed...");
    }, seconds * 1000)
  );

const tasks = [
  delay(1),
  delay(4),
  delay(8),
  delay(4),
  delay(7),
  delay(4),
  delay(10),
  delay(5),
  delay(0),
  delay(8),
  delay(1),
  delay(10),
  delay(7),
];

class ConcurrencyPromiseQueueExecutor {
  constructor(promises = [], concurrentExeCount = 1) {
    this.concurrent = concurrentExeCount;
    this.total = promises.length;
    this.todo = promises;

    this.running = [];
    this.completed = [];
  }

  get runAnother() {
    return this.todo.length && this.running.length < this.concurrent;
  }

  graphTasks() {
    var { todo, running, completed } = this;

    const state = {
      todo,
      running,
      completed,
    };

    console.log(JSON.stringify(state));
  }

  run() {
    while (this.runAnother) {
      var promise = this.todo.shift();
      this.running.push(promise);

      promise.then(() => {
        this.completed.push(this.running.shift());
        this.graphTasks();
        this.run();
      });

      this.graphTasks();
    }
  }
}

const promiseQueue = new ConcurrencyPromiseQueueExecutor(tasks, 3);
promiseQueue.run();