嵌套的依赖回调函数

//your call chain
getAccessToken()
  .then(getUserID)
  .then(getUserDetails)
  .then(postUserDetails)
  .then(() => {
    console.log("Done");
  })

//a mock of your code

//a utility to "simulate" the delay of a server call and return a Promise
function wait(delay) {
  return new Promise(resolve => setTimeout(resolve, delay));
}

function getAccessToken() {
  console.log("getAccessToken");
  //mock the request to the server
  return wait(Math.random() * 1000+500)
    .then(() => {
      console.log("generating a token");
      return Math.random().toString(36).slice(2)
    });
}

function getUserID(token) {
  console.log("getUserID(%o)", token);
  //mock the request to the server
  return wait(Math.random() * 1000+500)
    .then(() => {
      console.log("returning userId");
      return "id-1234";
    });
}

function getUserDetails(userId) {
  console.log("getUserDetails(%o)", userId);
  //mock the request to the server
  return wait(Math.random() * 1000+500)
    .then(() => {
      console.log("returning user");
      return {
        id: userId,
        firstName: "Zaphod",
        lastName: "Beeblebrox"
      }
    });
}


function postUserDetails(user) {
  console.log("postUserDetails(%o)", user);
  return wait(Math.random() * 1000+500)
    .then(() => {
      console.log("userDetails posted");
    });
}

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