CODEWITHSUNDEEP
node.js
gwendall
gwendall

Reputation: 920

Passing variables to all modules

I'm building a service which is fragmented across multiple modules that are required when necessary. I need to access the "request" variable from the router in all my modules.

My current solution (which has been suggested in other threads for passing variables in general) is to pass it to each required module:

var a_module = require('./a_module')(req);

And exporting each module as functions:

module.exports = function(req) { ... }

But it is verbose and involves having to export my modules as functions, and only having access to this variable in the scope of the exported functions. Ideally I would like to be able to access the variable across the entire required module.

Is there any other elegant way to do it that I am missing? Like declaring the req variable as a global across the entire application?

Upvotes: 3

Views: 466

Answers (1)

Peter Lyons
Peter Lyons

Reputation: 145994

This question is going to solicit opinions not answers, so it's not a great fit for stack overflow, but here's my $0.02.

You need to step back and ask yourself if you have really written so many modules that need access to a request object. I don't think you have. What you should be writing are functions that take the specific data they need - no more, no less. All these functions almost certainly don't need the entire request. How many of them really need access to every HTTP header, for example? Think of your program as a set of operations on domain objects/data. For example, maybe there's a function that takes a user account record and promotes it from a regular user to an administrator. All that function needs is the user account. It should not be coupled to an HTTP request object.

Just write a bunch of cleanly decoupled functions that take a small number of precise parameters and do something useful with them. This is called "loose coupling". Then organize groups of related functions into a module. This is called "cohesion". Then use some "glue" code to extract the necessary parameters from the HTTP req object and pass them as arguments to these functions. These same functions should work for a command line interface or another non-HTTP interface. They will be easier to understand, test, and more long-lived if you code them that way instead of going nuts with every line of every module knowing about the current HTTP req object.

Upvotes: 3

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