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callback（err）时，我的自定义异步回调被调用。在那里我抛出了一个错误，希望它能够在异步的try块中被捕获，但是这没有发生。

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

适合我。你看到有什么不同吗？如果有更多的话，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]: 

此代码：

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); 
} 

Answer 3

希望它会在周围异步try块被抓住，但没有发生

这是不可能的。错误将被创建并异步抛出，即在async.waterfall已返回并且try块被留下之后很久。如果您想处理异步错误，请在myAsyncCallback中执行（就像您已经这样做）。在异步回调中从不使用throw。