promise使用方法

1 let p = new Promise((resolve, reject) => {
2   throw new Error("我错了"); //会失败
3 })
4 
5 p.then((data) => {
6   console.log(data)
7 }, (err) => {
8   console.log(err) // 执行这个方法
9 })

let p = new Promise((resolve, reject) => {
  reject("我错了") //会失败
})

p.then((data) => {
  console.log(data)
}, (err) => {
  console.log(err) // 执行这个方法
})

let p = new Promise((resolve, reject) => {
  resolve("我对了") // 会成功
})

p.then((data) => {
  console.log(data) // 执行此方法
}, (err) => {
  console.log(err) 
})

let p = new Promise((resolve, reject) => {
  console.log("不知道");
})

p.then((data) => {
  console.log(data) // 不执行
}, (err) => {
  console.log(err)  // 不执行
})

let p = new Promise((resolve, reject) => {
  resolve("执行1")
})

p.then((data) => {
  return "执行2"
}).then((data) => {
  return "执行3"
}).then((data) => {
  console.log(data) //执行3
})

let p = new Promise((resolve, reject) => {
  resolve("执行1")
})

p.then((data) => {
  return new Promise((resolve, rejext) => {resolve("执行2")})
}).then((data) => {
  return new Promise((resolve, rejext) => {resolve("执行3")})
}).then((data) => {
  console.log(data) //执行3
})

let p = new Promise((resolve, reject) => {
  resolve("执行1")
})

p.then((data) => {
  // 跳过我吧！
}).then((data) => {
  return new Promise((resolve, rejext) => {resolve("执行3")})
}).then((data) => {
  console.log(data) //执行3
})