03回调函数

//回调函数
doSomeThing(result => {
  doSomeThingElse(result, newResult => {
    doSomeThingThird(newResult, finalResult => {
      console.log(finalResult)
    }, errCallback)
  }, errCallback)
}, errCallback)

// promise嵌套
doSomeThing()
  .then(result => {
    return doSomeThingElse(result)
  })
  .then(newResult => {
    return doSomeThingThird(newResult)
  })
  .then(finalResult => {
    console.log(finalResult)
  })
  .catch(err => {
    console.log(err);

  })
//异常穿透，只需要指定一个catch



async function request() {
  try {
    const result = await doSomeThing()
    const newResult = await doSomeThingElse(result)
    const finalResult = await doSomeThingThird(newResult)
    console.log(‘finalResult: ‘, finalResult);
  } catch (error) { //异常穿透
    errCallback(error) 
  }

}
let errCallback = error => {
  console.log(error)
}