Accessing global variables with node.js and CoffeeScript

Question

I'm trying to declare global variables for my applications that I'm writing using Node.js and CoffeeScript. So I'm declaring it in a common file that is concatenated to both applications after compilation. In that file I have for example:

root = exports ? this
root.myVariable = 300

So my first application is a HTML one. When I try to access this variable, for example by

console.log myVariable

There is no problem with it. But my other application is a server application lauched by node command and I cannot access that variable in that application. I tried:

console.log root.myVariable
console.log myVariable

With first line I'm getting 'undefined' printed (so it looks that root is defined) and with the second one, I'm getting ReferenceError - myVariable is undefined.

So how can I access this variable?

Here is an output code in Javascript that I get, I guess it might be helpful:

(function() {
  var root, _ref;

  root = (_ref = typeof module !== "undefined" && module !== null ? module.exports : void 0) != null ? _ref : this;

  root.myVariable = 300;

}).call(this);

(function() {

  console.log(root.myVariable);

  console.log(myVariable);

}).call(this);

You want to declare a global (generally mutable) variable in node.js, or you want to declare a constant (immutable) variable, that'll be accessible both from client and server js? — Leonid Beschastny
– Leonid Beschastny, Commented Mar 19, 2013 at 11:15
@leonid-beschastny Well, actually it should be a constant value read from both applications. — krajol
– krajol, Commented Mar 19, 2013 at 11:18

Mulan · Accepted Answer · 2022-01-24 15:37:59Z

2

You're close, but you need to change things just a little bit

# config.coffee
module.exports =
  foo: "bar"
  hello: "world"
  db:
    user: alice
    pass: password1

# lib/a.coffee
config = require "../config"

# lib/b.coffee
config = require "../config"

# lib/db.coffee
dbconfig = require("../config").db

edited Jan 24, 2022 at 15:37

answered Mar 19, 2013 at 15:29

Mulan

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1 Comment

Leonid Beschastny Over a year ago

module.exports will trow an exception on the client side.

Leonid Beschastny · Accepted Answer · 2013-03-19 12:38:00Z

0

Client and server JavaScript (or CoffeeScript) works differently. So, its a really difficult to write a module that'll work in both applications.

There is a lot of libraries to solve this problem, like RequireJS and Browserify.

But I have two simpler suggestions for your problem.

First one is to use JSON to store your global constants. On the server side you can simply require you JSON file:

root = require './config.json'

On the client side you may either parse it manually or serve it as pjson.

My second suggestion is to write really simple module that'll be compatible with both your applications. It'll look something like this:

root = 
  myVariable: 300
  myOtherVariable: 400

modulte.exports = root if module?.parent?

This code should be compatible with both node.js require function and browser <script> tag.

Update:

I just reread you question and realized, that you've did almost as I suggested. But your code looks fine to me. You may try to use module.export instead of its alias exports, it may help:

root = modulte?.exports ? this
root.myVariable = 300

But, as I said, your code looks fine to me as well.

edited Mar 19, 2013 at 12:38

answered Mar 19, 2013 at 11:39

Leonid Beschastny

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2 Comments

krajol Over a year ago

Thank you for your reply but unfortunately the result is still the same after using module.export. I updated my question with an output after Coffeescript compilation, maybe it could be useful.

Leonid Beschastny Over a year ago

@krajol, have you required your module before accessing it from your server code? root = require './root.coffee'?

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