ES6学习笔记（四）—— async 函数

asyncReadFile = async function () {
  var f1 = await readFile(‘/etc/fstab‘)
  var f2 = await readFile(‘/etc/shells‘)
  console.log(f1.toString())
  console.log(f2.toString())
}

function getDay () {
  return new Date().getDay()
}
const today = await getDay ()
// Uncaught SyntaxError: Unexpected identifier

async function getName () {
  return ‘wangxi‘
}
getName()
// Promise {[[PromiseStatus]]: "resolved", [[PromiseValue]]: "wangxi"}

async function getName () {
  return ‘wangxi‘
}
getName().then(value => console.log(value))
// wangxi

async function f() {
  await Promise.reject(‘出错了‘)
  await Promise.resolve(‘hello world‘) // 不会执行
}
f() 
// VM259:4 Uncaught (in promise) 出错了 

async function f() {
  try {
    await Promise.reject(‘出错了‘)
  } catch(e) {
  }
  return await Promise.resolve(‘hello world‘)
}
f().then(v => console.log(v)) 

async function f() {
  await Promise.reject(‘出错了‘).catch(e => console.log(e))
  await Promise.reject(‘又出错了‘).catch(e => console.log(e))
  return await Promise.resolve(‘hello world‘)
}
f().then(v => console.log(v))
// 出错了
// 又出错了
// hello world

async function f () {
  // 先后，先执行 getName() 再执行 getAge()
  const name = await getName()
  const age = await getAge()
  console.log(name, wangxi) // wangxi 25
  // 同时触发
  let [name1, age1] = await Promise.all([getName(), getAge()])
  console.log(name1, age1) // wangxi 25
}