ES6 承诺结算回调? [英] ES6 promise settled callback?

问题描述

无论我的 Promise 是否成功解决，我都想运行相同的操作.我不想将相同的函数绑定到 .then 的两个参数.难道没有像 jQuery 那样的 .always 吗?如果没有，我该如何实现?

I want to run the same action whether my Promise resolved successfully or not. I don't want to bind the same function to both args of .then. Isn't there a .always like jQuery has? If not, how do I achieve this?

推荐答案

难道没有像 jQuery 那样的 .always 吗?

不，(目前)没有.虽然有一个活动提案，所以也许是 ES2018.
是的，有:promise .finally() 是 ES2018 标准的一部分.

No, there's not (yet). Though there is an active proposal, so maybe ES2018.
Yes, there is: promise .finally() is part of the standard since ES2018.

如果没有，我该如何实现?

If not, how do I achieve this?

您可以像这样自己实现 finally 方法:

You can implement the finally method yourself like this:

Promise.prototype.finally = function(cb) {
    const res = () => this
    const fin = () => Promise.resolve(cb()).then(res)
    return this.then(fin, fin);
};

或更广泛地，将解析信息传递给回调:

or more extensively, with passing resolution information to the callback:

Promise.prototype.finally = function(cb) {
    const res = () => this
    return this.then(value =>
        Promise.resolve(cb({state:"fulfilled", value})).then(res)
    , reason =>
        Promise.resolve(cb({state:"rejected", reason})).then(res)
    );
};

两者都确保保持原始分辨率(当回调中没有异常时)并等待承诺.

Both ensure that the original resolution is sustained (when there is no exception in the callback) and that promises are awaited.

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