I want one master action to complete its job asynchronously and at the end of its job free its slaves so I wrote this tiny library.

master-and-slave.js

let master = () => {
  return new Promise( (resolve, reject) => {
    setTimeout(() => { resolve('ok'); }, 3000);
  });
}

let slaves = [
  {
    start: () => {
    console.log("loading")
    },
    end: () => {
      console.log("loading finished")
    }
  },
  {
    start:() => {
    console.log("other job")
  },
   end: () => {
     console.log('end other job')
   }
  }
];


let resolvers = [];

master().then(
  response => { 
    resolvers.forEach(({resolve, end}) => {resolve(); end();});
    console.log("master is finished");
  },
  error => console.log("this code should not failed")
);



slaves.forEach(({start, end}) => {
  new Promise( (resolve, reject) => {
    start();
    resolvers.push({resolve, end});
  })
});