我什么时候应该直接调用Promise.resolve（）？ [英] When should I call Promise.resolve() directly?

问题描述

我已经看到，原生ES6 Promise.resolve（）可以直接调用 - 作为静态方法。 Facebook在他们的Flux示例中使用它。

I've seen that the native ES6 Promise.resolve() can be invoked directly - as a static method. Facebook is using it that way in their Flux examples.

但在什么情况下我应该这样做？排队的东西？或者不是使用 window.setTimeout（）？

But in what case should I do that? To queue something? Or instead of using window.setTimeout()?

推荐答案

当您需要创建已解决的承诺时，调用 Promise.resolve（object）。例如，您可能有一个功能，可以从服务器开始下载资源或返回其缓存版本：

You should call Promise.resolve(object) when you need to create a promise that is already resolved. For example you may have a function that starts downloading a resource from the server or returns its cached version:

function getImage(imageUrl) {
    if (imageUrl in this.cache) {
        // no need to download, return immediately
        return Promise.resolve(this.cache[imageUrl]);
    } else {
        return new Promise(function(resolve, reject) {
            // start downloading and eventually resolve
        });
    }
}

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