节点异步和异常处理

Question

我正在使用异步瀑布。当我的一个函数调用回调（错误）时，我的自定义异步回调被调用。在里面我抛出一个错误，希望它会在异步的 try 块中被捕获，但那没有发生。

try {
    async.waterfall([function1, function2], myAsyncCallback);
}
catch(err) {
    console.log("THIS CODE IS NEVER EXECUTED.");
}

var function1 = function() {
...
   //some error occurs:
   callback(new Error(errMsg), errMsg);
...
}

var function2 = function() {
...
}

function myAsyncCallback(err, result) {
    console.log("This code gets executed.");
    if (err) {
            console.log("This code gets executed too.");
            throw new Error("I want this error caught at the top around the catch around async.waterfall()");
        }
}

Answer 1

https://runkit.com/imjosh/async-try-catch/2.0.0

var async = require('async');

try {
  async.waterfall([function1, function2], myAsyncCallback);
}
catch(err) {
  errorHandler(err);
}

function function1(callback) {
  console.log('in fn1')   
  callback(null,'fn1');   
}

function function2(fn1, callback) {
  console.log('in fn2')
  callback(null, fn1 + 'fn2');
}

function myAsyncCallback(err, result) {
    if (err) {
      console.error('There was an error: ' + err);
      return;
    }
    //an error occurs. this gets caught by the outer try block
    //var foo = outer; //oops, outer is not defined. This throws an error

    //same scenario but inside an async function
    //can't/won't be caught by the outer try block
    setTimeout(function(){ 
        try{ //need try here
          var foo = inner; //oops, inner is not defined. This throws an error
        } 
        catch(err) {
          errorHandler(err);
       }
    }, 1000);

    console.log('Result was: ' + result);
}

function errorHandler(err){ 
  //Make error handler a function that can be called from either catch
  console.log('caught error: ' + err);
}

Answer 2

希望它会在异步的 try 块中被捕获，但那没有发生

那是不可能的。错误将被异步创建和抛出，即在 async.waterfall 返回并离开 try 块之后很久。如果您想处理异步错误，请在myAsyncCallback 中执行（就像您已经做的那样）。永远不要在异步回调中使用throw。

Answer 3

为我工作。你看到有什么不同吗？如果有更多事情发生，我会更新我的答案。

这是我的输出：

[Clays-MacBook-Pro ~/Documents/workspace/scratch]:node index.js 
inside function1
This code gets executed.
This code gets executed too.
THIS CODE IS NEVER EXECUTED.
[Clays-MacBook-Pro ~/Documents/workspace/scratch]:node -v
v6.9.1
[Clays-MacBook-Pro ~/Documents/workspace/scratch]:

这段代码：

var async = require('async')
try {
    async.waterfall([function1, function2], myAsyncCallback);
}
catch(err) {
    console.log("THIS CODE IS NEVER EXECUTED.");
}

function function1(callback) {
    console.log("inside function1");
    var errMsg = "Uh oh";
   callback(new Error(errMsg), errMsg);
}

function function2(stuff2, callback) {
    console.log('inside function2');
    var errMsg = "Uh oh";
   callback(new Error(errMsg), errMsg);
}

function myAsyncCallback(err, result) {
    console.log("This code gets executed.");
    if (err) {
            console.log("This code gets executed too.");
            throw new Error("I want this error caught at the top around the catch around async.waterfall()");
        }
    console.log(result);
}