Promise的解析/拒绝功能的返回值 [英] Return value of Promise's resolve/reject functions

问题描述

考虑这种情况。

new Promise(function(resolve, reject) {
    var x = resolve(2);
});

x 的价值是多少？
我试图打印它，它显示我 undefined 。它很直观，但总是如此吗？是在文档吗？

What value will x be? I tried to print it and it showed me undefined. It is intuitive, but is it always so? Is it in docs?

第二个问题

new Promise(function(resolve, reject) {
    resolve(2);
    return 5;
});

我们应该从我们投入承诺的函数中返回什么？该值是否被忽略？

What should we return from the function that we put into a promise? Is this value ignored?

推荐答案

promise构造函数的返回值被忽略。

The return value of the promise constructor is ignored.

解决功能返回undefined 。

这首先在promise构造函数规范中指定，后来在ES2015中指定（ES6）语言规范。

This was first specified in the promise constructor spec and later in the ES2015 (ES6) language specification.

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