Async 非同步
Node.js Async 非同步
Categories:
Promise
什麽是 Promise?
Promise 是一个表示非同步运算的最终 完成
或 失败
的物件。Promise 物件会有三种状态::pending
初始状态 、 fulfilled
表示操作成功地完成 、 rejected
表示操作失败。如果我们需要依序串连执行多个 Promise 功能的话,可以透过 .then() 来做到。
The Promise object represents the eventual completion (or failure) of an asynchronous operation and its resulting value.
A promise may be in one of 3 different states: pending, fulfilled or rejected.
Promises help you naturally handle errors, and write cleaner code by not having callback parameters.
Async
什麽是 Async
async/await 其实是 promise 语法糖,让你可以用更简洁的方法达到非同步。(async function 本身就会回传 promise)
The async function is syntactic sugar for promise.