CODEWITHSUNDEEP
node.jsnode-modules
Bas van Dijk
Bas van Dijk

Reputation: 10703

Share data between modules in NodeJS

I am working on a home automation project in NodeJS with several modules. These modules need access to data devices within a central DeviceManager. Normally I would create a singleton for this purpose so all modules access the same state of the DeviceManager.

To create a singleton I use:

class DevicesManagerInstance {

    constructor() {

        this.devices = {};

    }

    addDevice(id, device) {
        this.devices.id = device;
    }

}

let DevicesManagerInstance = new DevicesManager();

module.exports = DevicesManagerInstance;

I've found some older questions regarding singletons and sharing data but still not satisfied with the answer to the question if it is de NodeJS way to share data:

But also read singletons are an anti-pattern. Can someone clarify what is the "NodeJS" way of sharing data between modules (in my case the devices). In Angular I would create a service for this purpose.

Upvotes: 2

Views: 6254

Answers (2)

Bharathvaj Ganesan
Bharathvaj Ganesan

Reputation: 3184

This is a single instance but if you need class you can also convert the following to class structure easily,

var DeviceManager = function() {
      this.devices: [];  // constructor
};

DeviceManager.prototype.addDevice = function(id, device) {
             DeviceManager.devices[id] = device;          
};
var deviceManager = new DeviceManager();
module.exports = deviceManager;

You can access the devices in other modules as 

var DeviceManager = require('./devicemanager');
DeviceManager.devices; // accessing devices

Upvotes: 2

EKW
EKW

Reputation: 2113

Why fix what isn't broken? If your approach works, it works.

That being said, I don't see any reason to create a class if I'm only going to create one instance. I would opt for a different approach:

var DeviceManager = {
    devices: {},
    addDevice(id, device) { // this is valid syntax
        DeviceManager.devices[id] = device;
    }
};
module.exports = DeviceManager;

or, if you don't want devices to be available outside of the module:

var devices = {};
var DeviceManager = {
    addDevice(id, device) { // this is valid syntax
        devices[id] = device;
    }
};
module.exports = DeviceManager;

Upvotes: 4

Related Questions