🍄Promise

JS ⟩ async ⟩ Promise

⭐️ ES6 (2015) the future result of an async operation.

let p = promise.then(onFulfilled, onRejected)

🔸 定義

if we have：

let p = promise.then(onResolved, onRejected)

we say p is：

• resolved if onResolved() is called.

  • fulfilled if onResolved() returns a non-Promise value.

• rejected if onRejected() is called.

• settled if it's fulfilled or rejected.

• pending if it's neither fulfilled nor rejected.

Any settled Promise has an associated value , which won't change.

🔴 主題

• using Promises

  • getJSON() - get JSON (Promise) from URL.

• error handling

  • recoverable errors

  • finally()

• chaining Promises

• Promises in parallel

👥 相關

• ⭐️ ES2018 - for-await, finally()

• await

• await promises

• Promise.wait()

• Promise.inSeries()

• Promises in parallel

• async function

• async method

📗 參考

• JavaScript: The Definitive Guide (13.2 Promises)

• amazon.jp ⟩ マンガでわかる JavaScript の Promise (Kindle Cloud Reader)

📘 手冊

• Promise.resolve()

• Promise.reject()