另一个答案，使用babel节点版本<6

使用async - await

NPM install -g babel@5.6.14

example.js:

async function getExample(){

  let response = await returnPromise();

  let response2 = await returnPromise2();

  console.log(response, response2)

}

getExample()

然后，运行babel-node example.js，瞧!

可变上下文状态

简单的(但不优雅且容易出错)解决方案是使用更高范围的变量(链中的所有回调都可以访问)，并在获得结果值时将结果值写入它们:

function getExample() {
    var resultA;
    return promiseA(…).then(function(_resultA) {
        resultA = _resultA;
        // some processing
        return promiseB(…);
    }).then(function(resultB) {
        // more processing
        return // something using both resultA and resultB
    });
}

人们也可以使用一个(初始为空的)对象来代替许多变量，结果将作为动态创建的属性存储在对象上。

这个解决方案有几个缺点:

Mutable state is ugly, and global variables are evil. This pattern doesn't work across function boundaries, modularising the functions is harder as their declarations must not leave the shared scope The scope of the variables does not prevent to access them before they are initialized. This is especially likely for complex promise constructions (loops, branching, excptions) where race conditions might happen. Passing state explicitly, a declarative design that promises encourage, forces a cleaner coding style which can prevent this. One must choose the scope for those shared variables correctly. It needs to be local to the executed function to prevent race conditions between multiple parallel invocations, as would be the case if, for example, state was stored on an instance.

Bluebird库鼓励使用传递的对象，使用bind()方法将上下文对象分配给承诺链。每个回调函数都可以通过不可用的this关键字访问它。虽然对象属性比变量更容易出现无法检测到的错别字，但该模式相当聪明:

function getExample() {
    return promiseA(…)
    .bind({}) // Bluebird only!
    .then(function(resultA) {
        this.resultA = resultA;
        // some processing
        return promiseB(…);
    }).then(function(resultB) {
        // more processing
        return // something using both this.resultA and resultB
    }).bind(); // don't forget to unbind the object if you don't want the
               // caller to access it
}

这种方法可以很容易地在不支持.bind的promise库中模拟(尽管以一种更详细的方式，并且不能在表达式中使用):

function getExample() {
    var ctx = {};
    return promiseA(…)
    .then(function(resultA) {
        this.resultA = resultA;
        // some processing
        return promiseB(…);
    }.bind(ctx)).then(function(resultB) {
        // more processing
        return // something using both this.resultA and resultB
    }.bind(ctx));
}

关于承诺，我学到的是只将其用作返回值，尽可能避免引用它们。Async /await语法对此特别实用。今天所有最新的浏览器和节点都支持它:https://caniuse.com/#feat=async-functions，是一个简单的行为，代码就像读取同步代码，忘记回调…

在我确实需要引用承诺的情况下，创建和解决发生在独立/不相关的地方。因此，我宁愿使用人工关联和事件侦听器来解析“远程”承诺，而更喜欢将承诺公开为Deferred，下面的代码在有效的es5中实现了它

/**
 * Promise like object that allows to resolve it promise from outside code. Example:
 *
```
class Api {
  fooReady = new Deferred<Data>()
  private knower() {
    inOtherMoment(data=>{
      this.fooReady.resolve(data)
    })
  }
}
```
 */
var Deferred = /** @class */ (function () {
  function Deferred(callback) {
    var instance = this;
    this.resolve = null;
    this.reject = null;
    this.status = 'pending';
    this.promise = new Promise(function (resolve, reject) {
      instance.resolve = function () { this.status = 'resolved'; resolve.apply(this, arguments); };
      instance.reject = function () { this.status = 'rejected'; reject.apply(this, arguments); };
    });
    if (typeof callback === 'function') {
      callback.call(this, this.resolve, this.reject);
    }
  }
  Deferred.prototype.then = function (resolve) {
    return this.promise.then(resolve);
  };
  Deferred.prototype.catch = function (r) {
    return this.promise.catch(r);
  };
  return Deferred;
}());

编译自我的一个typescript项目:

https://github.com/cancerberoSgx/misc-utils-of-mine/blob/2927c2477839f7b36247d054e7e50abe8a41358b/misc-utils-of-mine-generic/src/promise.ts#L31

对于更复杂的情况，我经常使用这些没有测试和输入依赖关系的小工具。P-map已经有用过几次了。我认为他涵盖了大多数用例:

https://github.com/sindresorhus?utf8=%E2%9C%93&tab=repositories&q=promise&type=source&language=

显式直通

类似于嵌套回调，此技术依赖于闭包。然而，链保持不变——不是只传递最新的结果，而是为每一步传递某个状态对象。这些状态对象累积先前操作的结果，传递稍后将再次需要的所有值加上当前任务的结果。

function getExample() {
    return promiseA(…).then(function(resultA) {
        // some processing
        return promiseB(…).then(b => [resultA, b]); // function(b) { return [resultA, b] }
    }).then(function([resultA, resultB]) {
        // more processing
        return // something using both resultA and resultB
    });
}

这里，小箭头b => [resultA, b]是在resultA上关闭的函数，并将两个结果的数组传递给下一步。它使用参数解构语法将其再次分解为单个变量。

在ES6提供解构之前，许多承诺库(Q, Bluebird, when，…)提供了一个漂亮的助手方法，名为.spread()。它接受一个带有多个参数的函数——每个数组元素一个参数——作为.spread(function(resultA, resultB) {....

当然，这里需要的闭包可以通过一些辅助函数进一步简化，例如。

function addTo(x) {
    // imagine complex `arguments` fiddling or anything that helps usability
    // but you get the idea with this simple one:
    return res => [x, res];
}

…
return promiseB(…).then(addTo(resultA));

或者，您可以使用Promise。所有这些都是为了产生数组的承诺:

function getExample() {
    return promiseA(…).then(function(resultA) {
        // some processing
        return Promise.all([resultA, promiseB(…)]); // resultA will implicitly be wrapped
                                                    // as if passed to Promise.resolve()
    }).then(function([resultA, resultB]) {
        // more processing
        return // something using both resultA and resultB
    });
}

你不仅可以使用数组，还可以使用任意复杂的对象。例如，用_。扩展或对象。在不同的helper函数中赋值:

function augment(obj, name) {
    return function (res) { var r = Object.assign({}, obj); r[name] = res; return r; };
}

function getExample() {
    return promiseA(…).then(function(resultA) {
        // some processing
        return promiseB(…).then(augment({resultA}, "resultB"));
    }).then(function(obj) {
        // more processing
        return // something using both obj.resultA and obj.resultB
    });
}

While this pattern guarantees a flat chain and explicit state objects can improve clarity, it will become tedious for a long chain. Especially when you need the state only sporadically, you still have to pass it through every step. With this fixed interface, the single callbacks in the chain are rather tightly coupled and inflexible to change. It makes factoring out single steps harder, and callbacks cannot be supplied directly from other modules - they always need to be wrapped in boilerplate code that cares about the state. Abstract helper functions like the above can ease the pain a bit, but it will always be present.

同步检查

将稍后需要的承诺值分配给变量，然后通过同步检查获得它们的值。这个例子使用了bluebird的.value()方法，但是很多库都提供了类似的方法。

function getExample() {
    var a = promiseA(…);

    return a.then(function() {
        // some processing
        return promiseB(…);
    }).then(function(resultB) {
        // a is guaranteed to be fulfilled here so we can just retrieve its
        // value synchronously
        var aValue = a.value();
    });
}

这可以用于任意多的值:

function getExample() {
    var a = promiseA(…);

    var b = a.then(function() {
        return promiseB(…)
    });

    var c = b.then(function() {
        return promiseC(…);
    });

    var d = c.then(function() {
        return promiseD(…);
    });

    return d.then(function() {
        return a.value() + b.value() + c.value() + d.value();
    });
}

打破枷锁

When you need to access the intermediate values in your chain, you should split your chain apart in those single pieces that you need. Instead of attaching one callback and somehow trying to use its parameter multiple times, attach multiple callbacks to the same promise - wherever you need the result value. Don't forget, a promise just represents (proxies) a future value! Next to deriving one promise from the other in a linear chain, use the promise combinators that are given to you by your library to build the result value.

这将导致一个非常直接的控制流程，清晰的功能组合，因此易于模块化。

function getExample() {
    var a = promiseA(…);
    var b = a.then(function(resultA) {
        // some processing
        return promiseB(…);
    });
    return Promise.all([a, b]).then(function([resultA, resultB]) {
        // more processing
        return // something using both resultA and resultB
    });
}

而不是在Promise之后的回调中进行参数解构。在ES5中，then调用将被许多承诺库(Q, Bluebird, when，…)提供的一个漂亮的助手方法所取代:.spread(function(resultA, resultB) {....

Bluebird还提供了一个专用的连接功能来取代承诺。All +扩展组合，更简单(更有效)的结构:

…
return Promise.join(a, b, function(resultA, resultB) { … });