Mock for ajax parallel requests

ajax-parallel-requests.js

const call = (function() {
  const maxParallelCalls = 5;
  let activeCalls = 0;
  let requestsStack = [];

  // outside promise proxy
  const Defer = function() {
    this.promise = new Promise((resolve, reject) => {
      this.resolve = resolve;
      this.reject = reject;
    });
  };

  // your library async call
  const axiosCall = data => {
    return new Promise((resolve, reject) => {
      console.log("start", data.path);

      setTimeout(() => {
        resolve([data.path, data.start, new Date()]);

        // handle new calls from stack
        activeCalls -= 1;
        handle();
      }, 0.1 + Math.random() * (4 + 1 - 0.1));
    });
  };

  // handler - make new requests
  const handle = () => {
    if (activeCalls >= maxParallelCalls) {
      return;
    }

    while (activeCalls < maxParallelCalls && requestsStack.length) {
      activeCalls += 1;
      const data = requestsStack.shift();
      axiosCall(data).then(r => data.defer.resolve(r));
    }
  };

  return function(type, path, query, body) {
    const data = {
      type,
      path,
      query,
      body,
      defer: new Defer(),
      created: new Date()
    };

    requestsStack.push(data);
    handle();
    return data.defer.promise;
  };
})();

const get = (path, query) => {
  return call("get", path, query);
};

const post = (path, query, body) => {
  return call("post", path, query, body);
};

let c = 50;
while (c) {
  c -= 1;
  get(`api/user/${c}`).then(resp => {
    console.log("FINALLY SUCCESS", resp[0]);
  });
}