let locked = false

const checkCanCall = (resolve)  => {
  if (locked) {
    return setTimeout(() => checkCanCall(resolve), 100)
  }
  locked = true
  resolve()
};

const waitUntilFree = () => new Promise(checkCanCall)

const unlock = () => locked = false

const synchronize = (action) => {
  return waitUntilFree()
    .then(() => action())
    .finally(unlock)
};


synchronize(() => {
  return new Promise((r) =>{
    setTimeout(r, 3000);
  }).then(r => {
    console.info('First Promise, after 3s')
  })
}).then(()=>{
  console.info('After first promise')
})

synchronize(() => {
  return new Promise((r) =>{
    setTimeout(r, 3000);
  }).then(r => {
    console.info('Second Promise, after 6s')
  })
}).then(()=>{
  console.info('After second promise')
})

console.info('Immediately executed, wait for 3s')