这是NodeJS中的变量范围错误还是我需要更多的睡眠 [英] Is this a variable scoping bug in NodeJS or do I just need more sleep

问题描述

在NodeJS项目上工作，我遇到了这个非常意想不到的行为，我无法解决这个问题 - 这对我来说似乎是个错误，但也许我只是误解了NodeJS模块的运作方式。

Working on a NodeJS project, I came a across this very unexpected behaviour that I can't figure a way around - it seems like a bug to me, but perhaps I'm simply misunderstanding how NodeJS modules operate.

我已将其缩减为测试用例，如下所示：

I've reduced it into a testcase as follows:

mod.js module

exports.process = function(obj) { obj.two = 'two'; };

test.js文件

var testObj = {one: 'one'};


console.log(['Before:', testObj]);

var cachedObj = testObj;
require('./mod').process(cachedObj);

console.log(['After:', testObj]);

然后运行 $ node test.js 给我这个：

[ 'Before:', { one: 'one' } ]
[ 'After:', { one: 'one', two: 'two' } ]

我将 testObj 的值分配给 cachedObj 和 testObj 永远不会传递给模块方法。 testObj 应该（据我所知）永远不会修改。

I'm assigning the value of testObj to cachedObj, and testObj is never being passed to the module method. testObj should (as far as I can see) never be modified at all.

实际上， cachedObj 也一定不会被修改，因为它永远不会从 mod.process 方法返回。我哪里错了？

In fact, cachedObj should surely never be modified either, as it is never returned from the mod.process method. Where am I going wrong?

（运行节点0.6.9）

(running Node 0.6.9)

推荐答案

这不是一个错误，它是完全预期的行为。

It's not a bug, it's perfectly expected behavior.

JavaScript中的变量通过引用传递，因此原始对象在<$ c $中的赋值变异c>处理。

Variables in JavaScript are passed by reference, so the original object is mutated by the assignment in process.

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