External js files

Developers
1

I have different modules is my file app.js I would like to separate these in an external js file per module. Now my question is how do I link an external file to the main app.js file and vice versa.

2

In app.js you use require() to load external JS files (“modules”).

Those external JS files need to explicitly export functions/classes/variables to make them available in app.js:

// library.js
module.exports.helloWorld = function() {
  console.log('hello world');
}

// app.js
const { helloWorld } = require('./library.js');
// or:
// const helloWorld = require('./library.js').helloWorld;

helloWorld();

Be aware that Node.js doesn’t support cyclic dependencies, meaning that if you load library.js into app.js you cannot also load app.js into library.js as well (because that introduces a cyclic dependency, where file A depends on file B which depends on file A which depends on file B etc)

More info here: Modules: CommonJS modules | Node.js v12.22.7 Documentation

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3

but is it possible to read variables from app.js into a module?

4

Your module should export functions that take arguments, and you pass those variables as arguments to the functions.

5

Check out a example. GitHub - mickelluiten/com.satelintegra: Satel Integra Alarmsystem integration with Homey
In folder JS you find functions.js that is used is the app.js , driver.js and devices.js.

6

I’ve looked at it but it’s too complex. Isn’t it possible to give a simple example of a function in a module with two variables (from app.js) processed in a module and sent back to app.js

7

Perhaps it’s more beneficial for you to find a Node.js tutorial that covers external modules and functions. This isn’t the right place to learn JS and Node.js specifics.

1 Like