这几天，我也遇到了一些像你一样的问题。最后，我用这个问题找到了一个很好的解决方案，它简单易懂。我希望这能帮助到你。

根据how-to-chain-javascript-promises

好的，让我们看看代码:

const firstPromise = () => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('first promise is completed');
            resolve({data: '123'});
        }, 2000);
    });
};

const secondPromise = (someStuff) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('second promise is completed');
            resolve({newData: `${someStuff.data} some more data`});
        }, 2000);
    });
};

const thirdPromise = (someStuff) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('third promise is completed');
            resolve({result: someStuff});
        }, 2000);
    });
};

firstPromise()
    .then(secondPromise)
    .then(thirdPromise)
    .then(data => {
        console.log(data);
    });

这几天，我也遇到了一些像你一样的问题。最后，我用这个问题找到了一个很好的解决方案，它简单易懂。我希望这能帮助到你。

根据how-to-chain-javascript-promises

好的，让我们看看代码:

const firstPromise = () => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('first promise is completed');
            resolve({data: '123'});
        }, 2000);
    });
};

const secondPromise = (someStuff) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('second promise is completed');
            resolve({newData: `${someStuff.data} some more data`});
        }, 2000);
    });
};

const thirdPromise = (someStuff) => {
    return new Promise((resolve, reject) => {
        setTimeout(() => {
            console.log('third promise is completed');
            resolve({result: someStuff});
        }, 2000);
    });
};

firstPromise()
    .then(secondPromise)
    .then(thirdPromise)
    .then(data => {
        console.log(data);
    });

我不打算在我自己的代码中使用这种模式，因为我不太喜欢使用全局变量。然而，在紧要关头它还是有用的。

用户是一个承诺的猫鼬模型。

var globalVar = '';

User.findAsync({}).then(function(users){
  globalVar = users;
}).then(function(){
  console.log(globalVar);
});

对“可变上下文状态”不那么苛刻的解释

对于您提出的问题，使用局部作用域对象来收集承诺链中的中间结果是一种合理的方法。考虑下面的代码片段:

function getExample(){
    //locally scoped
    const results = {};
    return promiseA(paramsA).then(function(resultA){
        results.a = resultA;
        return promiseB(paramsB);
    }).then(function(resultB){
        results.b = resultB;
        return promiseC(paramsC);
    }).then(function(resultC){
        //Resolve with composite of all promises
        return Promise.resolve(results.a + results.b + resultC);
    }).catch(function(error){
        return Promise.reject(error);
    });
}

Global variables are bad, so this solution uses a locally scoped variable which causes no harm. It is only accessible within the function. Mutable state is ugly, but this does not mutate state in an ugly manner. The ugly mutable state traditionally refers to modifying the state of function arguments or global variables, but this approach simply modifies the state of a locally scoped variable that exists for the sole purpose of aggregating promise results...a variable that will die a simple death once the promise resolves. Intermediate promises are not prevented from accessing the state of the results object, but this does not introduce some scary scenario where one of the promises in the chain will go rogue and sabotage your results. The responsibility of setting the values in each step of the promise is confined to this function and the overall result will either be correct or incorrect...it will not be some bug that will crop up years later in production (unless you intend it to!) This does not introduce a race condition scenario that would arise from parallel invocation because a new instance of the results variable is created for every invocation of the getExample function.

示例在jsfiddle上可用

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.

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!