JavaScript中來自Async Await的關鍵字“ await”僅適用於諾言嗎？

Question

當await寫入異步函數中時，例如-

let x = await doSomething()

doSomething函數是否必須返回Promise ？

Answer 1

它可能會返回任何內容，因為

let x = await doSomething()
// ... rest of your code

// is roughly equivalent

Promise
  .resolve(doSomething())
  .then(value => {
    let x = value

    // ... rest of your code
  })

但是，如果doSomething是異步的，則它必須返回“ thenable”內容，以便await可以實際工作

 const doSomething = () => ({ then(fn) { setTimeout(fn, 2000, 'hello') } }) const run = async () => { let msg = await doSomething() console.log(msg) } run().then(() => console.log('Done'))