Question

我正在努力使承诺有效，到目前为止，我偶然发现了这一点：

new Promise((resolve, reject) => {
    setTimeout(() => {
        return resolve()
    }, 400)
}).then(new Promise((resolve, reject) => {
    setTimeout(() => {
        return reject('some error')
    }, 100)
})).then(() => {
    console.log('All promises resolved')
}).catch((err) => {
    console.log('Error: ' + err)
})

我的理解是这个例子应该显示Error: some error，第一个承诺成功解决，第二个承担错误。但是当我运行它时（在节点9.7中，如果这很重要）我得到这个错误：

(node:10102) UnhandledPromiseRejectionWarning: some error
(node:10102) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:10102) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
All promises resolved

我的.catch()似乎没有用，它有问题吗？

Answer 1

你实际上是在传递承诺，而不是功能。

您应该像这样编写代码：

new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve()
    }, 400)
}).then(() => new Promise((resolve, reject) => {
    setTimeout(() => {
        reject(new Error('some error'))
    }, 100)
})).then(() => {
    console.log('All promises resolved')
}).catch((err) => {
    console.log('Error: ' + err)
})

链式承诺不会发现错误

1 个答案: