嵌套的回调和例外处理的NodeJS [英] Nested callbacks and exceptions handling in NodeJS

问题描述

我已经来到跨几个答案和意见建议，以避免嵌套的NodeJS回调。我相信有观点背后的强项，但我不能让它正常！

I have came cross several answers and comments suggesting to avoid nested callbacks in NodeJS. I believe there is a strong point of view behind that but I can not get it properly!

让我们假设我有以下的code

Let's assume that I have the following code

module1.func1(
    function(){
        //some code
        module2.func2(
            function(){
                //some code
                module3.func3(etc....)
            }
        );
    }
);

现在让我们假设code我会在回调写会引起那么一个异常尝试和catch必须添加到code

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

module1.func1(
    function(){
        try{
            //some code
            module2.func2(
                function(){
                    try {
                        //some code
                        module3.func3(etc....)
                    } catch (ex){//handle exception}
                }
            );
        } catch(e){//handle exception}

    }
);

现在，我不仅有嵌套的回调，但也有例外的，处理的回调而增加的内存更多的开销！

Now, I'm not only having nested callbacks but also with exceptions-handled callbacks which add more overhead on memory!

有人会建议使用步，异步，等待换，但我不相信他们是从性能的角度很好的解决方案，因为它们只提供简单的语法，就是这样。纠正我，如果我错了。

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. Correct me if I'm wrong.

有什么办法避免这样的问题呢？改善回调-nested- code的表现呢？

Is there any way to avoid such problem? to improve performance of callbacks-nested-code?

推荐答案

承诺自动传播异步和同步错误

Promises automatically propagate both asynchronous and synchronous errors

这是什么意思？

这意味着code的回调code愿望的正确传播错误：

It means code that callback code that wishes to propagate errors properly:

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);
}

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];
});

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