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I'm using Node.js to run background jobs (no frontend). I think the best way for me to run the workers is to have one file for each kind of job (like that I can easily run one worker per server).

main.js

require('scribe-js')(); // github.com/bluejamesbond/Scribe.js
process.console = console;
...

worker_*.js

require('./lib/main');

console.tag('testing').log('this is a test');

The console variable isn't passed to worker_*.js. I to set it in main.js because if the value of the variable ever changes I want to be able to change it only once (in main.js) and not in each worker_*.js file. Any idea?

I think this is not a duplicate: I know there's plenty of "how do I include a JS file in another JS file in Node.js" and the answer is usually "use var s = require('yourfile');". I think this question is a bit different.

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  • Note: I would rather be using a mini framework but most like Express concentrate on having a frontend. Know of any mini framework? Commented Feb 3, 2015 at 3:57
  • The issue is that for each of my worker_*.js files I would need to write process.console = globals.customConsole; instead of just having it once in my main.js file. I'm trying to figure out a solution so I only define it once and it's available to all workers that include main.js. edit: weird, one of the comments disappeared Commented Feb 3, 2015 at 4:03
  • I turned my comment into an answer. That's why I deleted the comment. Commented Feb 3, 2015 at 4:05
  • Ah ok, I'll check the answer. Commented Feb 3, 2015 at 4:11

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To share a variable between node modules, you can:

  1. Export a method for the module, then call that method and pass it the variable you want to share or
  2. You can make the variable global.

The preferred method is to explicitly share a variable via an exported method and then let the module store its own copy of the variable. See here for info about globals.

In your case, it might make a lot of sense to support a common constructor for each worker and pass the worker an object that you can put properties on to share the same variables to each worker.

So, you'd so something like this:

worker_1.js

var savedArgs;
module.exports = function(args) {
    savedArgs = args;
}

And, then when worker_1.js was loaded, you'd do this:

var args = {console: process.console};
require('./worker_1.js')(args);

The design of modules is to be as self-contained as possible (e.g. not rely on global state) to encourage modularity and reusability. They should require() in what they need and any app configuration or singletons that they need in order to do their job that are created by other modules should be given to them in their constructor or via some other exported method.

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6 Comments

The second code block would be main.js? Therefore including worker_1.js in main.js rather than the other way around?
@iDev247 - I did not follow how you were using worker_1.js. I thought you were loading workers from one central module so that's how I coded it, but you can do things the other way around. You can load the shared module into the worker and then query it for it's singleton data by calling an exported method on it. The data can be pulled (you call someone else's exported method to get the data) or pushed (someone calls your constructor and gives you the data), depending upon how you have things structured. Either way works fine.
Got it! It looks like I would still need to do savedArgs.console.log() instead of console.log(). Is this right? I'd really like to find a solution where I can just do console.log() so that it's a universal change for all debugging.
Agree with @iDev247, wrap your console to some method or variable and use module.exports in main.js
Look like there might not be a way to define console globally without using globals. What I might do (which isn't really what I wanted to do): require('./lib/main')(function(console){...worker code...}) and in main.js I'll just return console as an argument.
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