64.Promise.resolve.js

Promise.myResolve = function (value) {
  if (value && typeof value === 'object' && (value instanceof Promise)) {
    return value
  }

  return new Promise((resolve) => {
    resolve(value)
  })
}
// 1. 非Promise对象，非thenable对象
Promise.resolve(1).then(console.log) // 1
// 2. Promise对象成功状态
const p2 = new Promise((resolve) => resolve(2))
Promise.resolve(p2).then(console.log) // 2
// 3. Promise对象失败状态
const p3 = new Promise((_, reject) => reject('err3'))
Promise.resolve(p3).catch(console.error) // err3
// 4. thenable对象
const p4 = {
  then (resolve) {
    setTimeout(() => resolve(4), 1000)
  }
}
Promise.resolve(p4).then(console.log) // 4
// 5. 啥都没传
Promise.resolve().then(console.log) // undefined

// Promise.myResolve(1).then((res) => {
//   console.log(res)
// })

// Promise.myResolve(new Promise((resolve, reject) => {
//   reject(1)
// })).then((res) => {
//   console.log(res)
// }).catch((err) => {
//   console.log(err, 'err')
// })