在即将到来的ECMAScript
2016（ES7）标准中，提供了一组新的语言关键字，这些关键字旨在执行与您似乎正在寻找的目标非常相似的操作，称为async和await。

这些关键字 不会 允许“非阻塞同步AJAX”，但他们让你的方式，编写异步代码 看起来 同步。这是一个简单的例子：

// Let's say you have an asynchronous function that you want to call in a synchronous
// style...
function delayedEval(delay, func) {
  // First, ensure that the function returns a Promise object. If it doesn't, wrap it with
  // another function that does.
  return new Promise((resolve, reject) => {
    setTimeout(() => resolve(func()), delay)
  })
  // For more on Promises, see https://goo.gl/uaoDuy (MDN link)
}

// Then, declare a function as asynchronous. This causes it to return a Promise that 
// resolves to its return value, instead of returning its return value directly.
async function delayedHello() {
  // Inside an async function, you can call other async functions like this, which looks
  // very much like a synchronous call (even though it isn't).
  let message = await delayedEval(1500, () => "Hello, world!")
  console.log(message)
}

// This returns (a Promise) immediately, but doesn't print "Hello, world!" until 1.5
// seconds later. (At which point it resolves the Promise.)
delayedHello()

尝试通天塔

基本上，而不是“无不良副作用同步AJAX”，async并await让你 异步 AJAX没有所有 的
负面影响。（具有许多用于处理回调的逻辑的混乱代码。）

async并且await是ES7标准中“异步功能”候选推荐的一部分。