Node.js引用module.exports

Question

I'm trying to do some js code shared between the browser and the nodejs server. To do that, I just use these practises: http://caolanmcmahon.com/posts/writing_for_node_and_the_browser/

The problem is when I want to export a function, not an object. In node you could do something like:

var Constructor = function(){/*code*/};
module.exports = Constructor;

so that when require is used you can do:

var Constructor = require('module.js');
var oInstance = new Constructor();

The problem is when I try to reference the module.exports object in the module and use that reference to overwrite it with my function. In the module it would be:

var Constructor = function(){/*code*/};
var reference = module.exports;
reference = Constructor;

Why this doesn't work? I don't want to use the easy solution to insert an if inside the clean code, but i want to understand why it is illegal, even though reference===module.exports is true.

Thanks

Answer 1

It does not work because reference does not point to module.exports , it points to the object module.exports points to:

module.exports
              \ 
                -> object
              / 
     reference

When you assign a new value to reference , you just change what reference points to, not what module.exports points to:

module.exports
              \ 
                -> object

reference -> function

---

Here is simplified example:

var a = 0;
var b = a;

Now, if you set b = 1 , then the value of a will still be 0 , since you just assigned a new value to b . It has no influence on the value of a .

i want to understand why it is illegal, even though reference===module.exports is true

It is not illegal , this how JavaScript (and most other languages) work. reference === module.exports is true, because before the assignment, they both refer to the same object. After the assignment, references refers to a different object than modules.export .