在功能范围之外解决Javascript Promise [英] Resolve Javascript Promise outside function scope

问题描述

我一直在使用ES6 Promise。

I have been using ES6 Promise.

通常，Promise的构造和使用就像这样

Ordinarily, a Promise is constructed and used like this

new Promise(function(resolve, reject){
    if (someCondition){
        resolve();
    } else {
        reject();
    } 
});

但为了灵活性，我一直在做类似下面的事情来解决问题。

But I have been doing something like below to take the resolve outside for the sake of flexibility.

var outsideResolve;
var outsideReject;
new Promise(function(resolve, reject) { 
    outsideResolve = resolve; 
    outsideReject = reject; 
});

以后

onClick = function(){
    outsideResolve();
}

这种方法很好，但是有更简单的方法吗？如果没有，这是一个好习惯吗？

This works fine, but is there an easier way to do this? If not, is this a good practice?

推荐答案

不，没有其他方法可以做到这一点 - 我唯一可以说的是这个用例不是很普通的。就像Felix在评论中所说的那样 - 你所做的将会一直有效。

No, there is no other way to do this - the only thing I can say is that this use case isn't very common. Like Felix said in the comment - what you do will consistently work.

值得一提的是，promise构造函数的行为方式就是抛出安全 - 如果你做了一个例外当你的代码在promise构造函数中运行时，预期不会发生，它会变成拒绝，这种抛出安全形式 - 将抛出的错误转换为拒绝是很重要的，有助于维护可预测的代码。

It's worth mentioning that the reason the promise constructor behaves this way is throw safety - if an exception you did not anticipate happens while your code is running inside the promise constructor it will turn into a rejection, this form of throw safety - converting thrown errors to rejections is important and helps maintain predictable code.

对于这个抛出安全的原因，promise构造函数被选择为延迟（这是一种替代的承诺构造方式，允许你正在做的事情） - 至于最佳实践 - 我将传递元素并使用promise构造函数相反：

For this throw safety reason, the promise constructor was chosen over deferreds (which are an alternative promise construction way that do allow what you're doing) - as for best practices - I'd pass the element and use the promise constructor instead:

var p = new Promise(function(resolve, reject){
    this.onclick = resolve;
}.bind(this));

出于这个原因 - 只要你可以使用promise构造函数而不是导出功能 - 我建议你使用它。每当你可以避免两者 - 避免两者和链。

For this reason - whenever you can use the promise constructor over exporting the functions - I recommend you do use it. Whenever you can avoid both - avoid both and chain.

注意，你不应该使用promise构造函数来处理 if（condition），第一个例子可以写成：

Note, that you should never use the promise constructor for things like if(condition), the first example could be written as:

var p = Promise[(someCondition)?"resolve":"reject"]();

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