schedules running HTTP requests

requestsManager.js

/**
 * @module
 * @description It schedules running HTTP requests
 */
export const requestsManager = (function() {
  const waitingQueue = [];
  const runningQueue = [];
  const MAX_PARALLEL_REQUESTS = 5;

  function makeRequest(reqToMake) {
    if (runningQueue.length < MAX_PARALLEL_REQUESTS) {
      runRequest(reqToMake);
    } else {
      waitingQueue.push(reqToMake);
    }
  }

  function runRequest(reqToMake) {
    const promise = reqToMake()
      .then(res => {
        runningQueue.splice(runningQueue.indexOf(promise), 1);

        if (waitingQueue?.length) {
          runRequest(waitingQueue[0]);
          waitingQueue.splice(0, 1);
        }

        return res;
      }).catch(err => {
        runningQueue.splice(runningQueue.indexOf(promise), 1);
        
        if (waitingQueue?.length) {
          runRequest(waitingQueue[0]);
          waitingQueue.splice(0, 1);
        }
      });
    
    runningQueue.push(promise);
  }

  return {
    makeRequest
  };
})();

requestsManager.makeRequest(new Promise((resolve, reject) => { fetch().then((res) => { resolve(res); }).catch((err) => { reject(err); }); }));