解决承诺而不叫'then' [英] Resolving a Promise without calling the 'then'

问题描述

我有这段代码，这是我为名为Poolio的NPM模块编写的小型API的一部分。对于那些支持错误优先回调和Promise的人来说，我似乎是一个常见问题。在维护一致的API和API一致的返回值的同时，我们如何支持两者？例如，如果我有条件地从我的API中返回一个promise，这取决于我的lib的使用者是否提供了回调，那么我认为这有点尴尬。

I have this code that is part of a small API that I am writing for an NPM module called Poolio. The question I have seems to be a common question for those supporting error-first callbacks as well as promises- how do we support both while maintaining consisent APIs and consistent return values from the API? For example, if I conditionally return a promise from my API, depending on whether the consumer of my lib provides a callback, that is a little awkward in my opinion.

lib的使用者可以提供回调或使用Promise then函数，但不能同时使用两者。

The consumer of the lib can provide a callback or use the Promise then function, but not both.

这里是我的lib导出的一个函数，谨在此声明：

Here is a function exported by my lib, that I would like to promisify:

Pool.prototype.any = function (msg, cb) {

    var workId = this.counter++;
    var self = this;

    return new Promise(function (resolve, reject) {

        if (typeof cb === 'function') {
            self.resolutions.push({
                workId: workId,
                cb: cb
            });
        }
        else {
            self.resolutions.push({
                workId: workId,
                resolve: resolve,
                reject: reject
            });
        }

        if (this.available.length > 0) {
            var cp = this.available.shift();
            cp.workId = workId;
            cp.send(msg);
        }
        else {
            self.msgQueue.push({
                workId: workId,
                msg: msg
            });
        }
    });

};

我的问题是-如果用户在原始函数参数中提供了回调函数，我该如何解决诺言而不叫那么？
对不起，很难解释，但希望您能理解。

my question is - if the user provides a callback function in the original function arguments, how can I resolve the promise without calling 'then'? Sorry it's hard to explain but hopefully you can understand.

还有一个有趣的问题：
从不解决的诺言会导致内存泄漏吗？

also there is this interesting question: Do never resolved promises cause memory leak?

推荐答案

实际上非常简单。

基本上，您可以这样做：

Basically you do this:

var promise = new Promise(function (resolve, reject) { /*....*/});

if (typeof cb === 'function') {
    promise.then(cb);
} else {
    return promise;
}

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