節點異步和異常處理

Question

我正在使用異步瀑布。當我的一個函數調用callback（err）時，我的自定義異步回調被調用。在那裏我拋出了一個錯誤，希望它能夠在異步的try塊中被捕獲，但是這沒有發生。

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

適合我。你看到有什麼不同嗎？如果有更多的話，我會更新我的答案。

這是我的輸出：

[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]: 

此代碼：

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

希望它會在周圍異步try塊被抓住，但沒有發生

這是不可能的。錯誤將被創建並異步拋出，即在async.waterfall已返回並且try塊被留下之後很久。如果您想處理異步錯誤，請在myAsyncCallback中執行（就像您已經這樣做）。在異步回調中從不使用throw。