Typescript - How to declare global variables on node.js

Question

How to declare some custom variables globally?

Usage Example

import './logger'; // custom module: Global logger is initialized. (using winston)

log.info('This is custom global logger.'); // access to log variable globally.

maybe globalThis? developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/… — Shanon Jackson
– Shanon Jackson, Commented Oct 14, 2019 at 2:25

Senthil · Accepted Answer · 2019-10-14 04:52:30Z

3

In TypeScript, declare global block's are used to describe to add a variable to global namespace or declare a global variables.

Node.js

import * as io from 'socket.io';

declare global {
  namespace NodeJS {
    interface Global {
      SocketServer: io.Server
    }
  }
}

global.SocketServer = io.default();

Note : Global variables are fine in some cases, even with multiple processes. Its recommended / commonly used when we have want to store a constant values, example some email ids during failures ex. global.support_email = "[email protected]"

Ref might be duplicate:

How to use global variable in node.js?

How to create writable global variable in node.js typescript (Using Typescript)

How to use global variable in node.js?

answered Oct 14, 2019 at 4:52

Senthil

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2 Comments

Kunie Over a year ago

Thank you. I solved. In my case,

import * as winston from 'winston'; declare global {  namespace NodeJS { interface Global { log: typeof winston.Logger; } } const log: winston.Logger; }

Senthil Over a year ago

Thats great to hear

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