cajames / global-const Goto Github PK

A lightweight utility to create global singletons (on browser and node)

• Works in Node and the browser
• Namespace in global object to prevent collision if multiple projects use this.
• Globally reference any kind of variable, object/function
• TypeScript support

To install global-const, use npm or yarn as follows:

npm install global-const
# or
yarn add global-const

import { getGlobalisedValue, clearGlobalNamespace } from "global-const";

const targetFunction = (someParams) => {
  // some function that maintains state, or works
  // within a closure.
};

const singletonInstance = getGlobalisedValue(
  "namespace",
  "targetFunction",
  targetFunction
);

// ...
singletonInstance("...");

// ... somewhere else in code

// this will get the same function instance as above
const anotherInstance = getGlobalisedValue(
  "namespace",
  "targetFunction",
  targetFunction
);

expect(singletonInstance).toBe(anotherInstance); // true

While it's generally not advised to add code to the global-state (window/globalThis), you might need to. This library comes handle to manage this.

And example is when you have many packages, each using a "metrics" module. When a customer individually instantiates each module, each module will probably instantiate it's own metrics tracking module. However if you wish for all the features to use the same metrics tracking function, instead of being siloed, this feature will help ensure that each time the metrics functions are instantiated, they'll check if there's one that's been globalised, and if so return that one instead.

• namespace: A unique string identifier to prevent collisions when considering other packages using this module.
• key: The name of the value to retrieve or set.
• value: An object/function to be globalised if it doesn't already exist.

Returns the globalised value or stores the value passed in if not initialised, and returns it.

const logger = getGlobalisedValue("myApp", "logger", new Logger());

• namespace: A unique string identifier to prevent collisions when considering other packages using this module.

This function is used for an application to clear out it's namespace.