如果序列中的承诺之一抛出错误，则按顺序解决承诺并打破序列

Question

假设我async设置了三个函数，如下所示：

const stepOne = async () => { setTimeout(function() {

  console.log("step 1")

}, 3000)  }

const stepTwo = async () => { throw new Error("Error at step two") }

const stepThree = async () => { console.log("step 3") }

我将如何按顺序执行所有这些函数并在 stepTwo 处打破承诺链，不允许 stepThree 函数运行？

所以，

正常顺序是这样的：stepOne --> stepTwo --> stepThree

在 stepTwo 处抛出错误的序列：stepOne --> stepTwo

在 stepTwo 抛出的错误需要在 end catch 块中被捕获。

更新#1：错过了问题的关键要素。await 不能使用，因为这三个函数需要在非异步函数中调用。

例子：

const testFunc = () => { 

  

  resolve three promises 

  sequentially, break the promise chain when error is thrown 

  and ultimately, catch errors here

   

  }

Answer 1

如果您解决承诺，您的代码将起作用stepOne，因为setTimeout只是将函数添加到堆栈而不是等待它解决。如果您要返回一个 PromisestepOne并在之后解决它，console.log那么它将try catch等待stepOne并捕获错误stepTwo这是您的代码示例const stepOne = async () => {    return new Promise((resolve, reject) => {        setTimeout(function() {            console.log("step 1")            resolve(true);        }, 3000)    });}const stepTwo = async () => { throw new Error("Error at step two") }const stepThree = async () => {    return new Promise((resolve, reject) => {        setTimeout(function() {            console.log("step 3")            resolve(true);        }, 3000)    });}(() => {    stepOne()        .then(stepTwo)        .then(stepThree)        .catch(error => {            console.log(error);        })  })();现在console.log看起来像这样step 1Error: Error at step two    at stepTwo (/home/user/develop/test/stackoverflow.js:10:38)    at processTicksAndRejections (internal/process/task_queues.js:93:5)

Answer 2

请尝试以下代码。您需要等待每次调用（stepOne、stepTwo 和 stepThree），以便在出现异常时不会进行下一次调用。try {    await stepOne();    await stepTwo();    await stepThree()} catch (error) {    console.log(error);}

Answer 3

如果您的步骤是返回 Promise 的函数，您可以创建一个包装函数，它将按顺序调用每个步骤并在步骤失败时中止，并记录失败步骤的详细信息。在此示例中，每个步骤失败的概率为五分之一。// Make a step proc, that throws 1 time in 5function createStep(index) {&nbsp; &nbsp; let error = (Math.random() < 0.2) ? new Error(`Step ${index+1} error`) : null ;&nbsp; &nbsp; return () => new Promise((resolve, reject) => setTimeout(error ? reject(error): resolve(`Step ${index+1} outcome`), 500));}async function runSteps(steps) {&nbsp; &nbsp;&nbsp; &nbsp;for(stepIndex = 0; stepIndex < steps.length; stepIndex++) {&nbsp; &nbsp; &nbsp; &nbsp;try {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;console.log(`Running step #${stepIndex+1}...`);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;let result = await steps[stepIndex]();&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;console.log(`Step result:`, result);&nbsp; &nbsp; &nbsp; &nbsp;} catch (e) {&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;console.error(`An error occurred at step #${stepIndex+1}:`, e.message);&nbsp; &nbsp; &nbsp; &nbsp; &nbsp;break;&nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp; &nbsp; &nbsp;if (stepIndex === (steps.length -1) ) {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; console.log("All steps completed successfully");&nbsp; &nbsp; &nbsp; &nbsp;}&nbsp; &nbsp;}}let steps = Array.from( { length: 3 }, (v,k) => createStep(k));runSteps(steps);