[英]Nested callbacks and exceptions handling in NodeJS
I have came cross several answers and comments suggesting to avoid nested callbacks in NodeJS. 我遇到了一些答案和评论,建议避免在NodeJS中嵌套嵌套的回调。 I believe there is a strong point of view behind that but I can not get it properly! 我相信这背后有很强的观点,但我无法正确理解!
Let's assume that I have the following code 假设我有以下代码
module1.func1(
function(){
//some code
module2.func2(
function(){
//some code
module3.func3(etc....)
}
);
}
);
Now let's assume that the code I would write in the callback may cause an exception then try and catch must be added to the code 现在,假设我要在回调中编写的代码可能会导致异常,然后必须将catch和catch添加到代码中
module1.func1(
function(){
try{
//some code
module2.func2(
function(){
try {
//some code
module3.func3(etc....)
} catch (ex){//handle exception}
}
);
} catch(e){//handle exception}
}
);
Now, I'm not only having nested callbacks but also with exceptions-handled callbacks which add more overhead on memory! 现在,我不仅具有嵌套的回调,而且还具有异常处理的回调,这会增加内存开销!
Some would suggest using step, async, wait-for but I don't believe they are good solutions from performance perspective as they only provide simpler syntax and that's it. 有人会建议使用step,async,wait-for,但是从性能的角度来看,我不认为它们是好的解决方案,因为它们仅提供了更简单的语法。 Correct me if I'm wrong. 如果我错了纠正我。
Is there any way to avoid such problem? 有什么办法可以避免这种问题? to improve performance of callbacks-nested-code? 提高回调嵌套代码的性能?
Promises automatically propagate both asynchronous and synchronous errors 承诺会自动传播异步和同步错误
What does that mean? 这意味着什么?
It means code that callback code that wishes to propagate errors properly: 这表示希望正确传播错误的回调代码的代码:
try {
doStuff1(function(err, value) {
if (err) return caller(err);
try {
doStuff2(value, function(err, value2) {
if (err) return caller(err);
try {
doStuff3(value2, function(err, value3) {
if (err) return caller(err);
caller(null, [value3]);
});
} catch(e) {
caller(e);
}
});
} catch (e) {
caller(e);
}
})
} catch (e) {
caller(e);
}
Can be replaced with: 可以替换为:
// Returning a value normally to the caller
return doStuff1()
.then(function(value) {
return doStuff2(value);
})
.then(function(value2) {
return doStuff3(value2);
})
.then(function(value3) {
return [value3];
});
试用Node.js域核心模块: http : //nodejs.org/api/domain.html
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