节点 8.6 javascript 承诺:UnhandledPromiseRejectionWarning [英] node 8.6 javascript promises: UnhandledPromiseRejectionWarning

问题描述

我有一个错误:(node:6186) UnhandledPromiseRejectionWarning: Unhandled promise Rejection (rejection id: 1): Threep(节点:6186)[DEP0018] 弃用警告:不推荐使用未处理的承诺拒绝.将来，未处理的承诺拒绝将以非零退出代码终止 Node.js 进程.-------- 那些======== 两个CaughtCathchError 三点(node:6186) PromiseRejectionHandledWarning: Promise 拒绝被异步处理 (rejection id: 1)我正在以嵌套顺序使用我的 3 个承诺函数.p1,p2,p3- 是我的承诺函数，如下所示.我也尝试在所有 p1、p2、p3 函数中添加承诺拒绝，但它仍然相同

I am having an error: (node:6186) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): threep (node:6186) [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. -------- ones ========= two CaughtCathchError threep (node:6186) PromiseRejectionHandledWarning: Promise rejection was handled asynchronously (rejection id: 1) I am consuming my 3 promise functions in nested order. p1,p2,p3- are my promise functions as shown below. i tried adding promise reject in all p1,p2,p3 functions as well but its still the same

enter code here
var p1 = new Promise(function (resolve, reject) {
    setTimeout(function () {
       // resolve('ones')
                resolve('ones')
    }, 9000)
})
var p2 = new Promise(function (resolve, reject) {
    setTimeout(function () {
        // throw new Error('eeeee');
        //reject('two')
    resolve('two')
    }, 1000)
})
var p3 = new Promise(function (resolve, reject) {
    setTimeout(function () {
        reject('three')
    }, 4000)
})

p1.then(function(result){
    console.log("--------", result)
        // return p2.then(function(res){console.log(res)}).catch(function(err){console.log(err)})
        return p2
}).then(function(p2result){
    console.log("=========", p2result)
    return p3;
}).then(function(p3result){
    console.log('*********', p3result)
}).catch(function(err){
    console.log("CaughtCathchError", err)
})

推荐答案

p3 是一个 独立的 Promise，没有 .catch.所以，当 p3 得到 reject ed 时，你会得到一个 UnhandledPromiseRejectionWarning.即使 p3 在具有正确 catch 的 Promise 链中稍后被消耗，p3 本身没有 catch.

p3 is a standalone Promise with no .catch. So, when p3 gets rejected, you get a UnhandledPromiseRejectionWarning. Even if p3 is consumed later in a Promise chain that has a proper catch, p3 itself does not have a catch.

代替 p3，您可以使用返回 Promise 的 函数，并确保捕获对该函数的所有调用:

Instead of p3, you might use a function that returns a Promise, and ensure that all calls to that function are caught:

var p1 = new Promise(function (resolve, reject) {
    setTimeout(function () {
       // resolve('ones')
                resolve('ones')
    }, 1000)
})
var p2 = new Promise(function (resolve, reject) {
    setTimeout(function () {
        // throw new Error('eeeee');
        //reject('two')
    resolve('two')
    }, 1000)
})
var getp3 = () => new Promise(function (resolve, reject) {
    setTimeout(function () {
        reject('three')
    }, 1000)
})

p1.then(function(result){
    console.log("--------", result)
        // return p2.then(function(res){console.log(res)}).catch(function(err){console.log(err)})
        return p2
}).then(function(p2result){
    console.log("=========", p2result)
    return getp3();
}).then(function(p3result){
    console.log('*********', p3result)
}).catch(function(err){
    console.log("CaughtCathchError", err)
})

如果你需要立即初始化p3，那么在p3本身之后放一个catch.

If you need to initialize p3 immediately, then put a catch after the p3 itself.

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