什么是回调地狱以及promise的链式调用和aysnc/await

doSomething(function(result){
  doSomethingElse(result, function(newResult){
    doThirdthing(newResult, function(finalResult){
      console.log('finial result'+finalResult)
      },failureCallback)
    },failureCallback)
  },failureCallback)

doSomething().then(function(result){
  return doSomethingElse(result)
 })
 .then(function(newResult){
    return doThirdThing(newResult)
  })
  .then(function(finalResult){
    console.log('final result'+finalResult)
    })
    .catch(failureCallback)

async func request(){
  try{
  const result = await doSomething()
  const newResult = await doSomethinElse(result)
  const finalResult = await doThirdThing(newResult)
  console.log('final result'+finalRequest)
  }catch(error){
  failureCallback(error)
  }
  }