How to create writable global variable in node.js typescript

问题

I have declared a global variable

import * as io from "socket.io";

declare let SocketServer: io.Server

and tried to write in another file but this variable is read-only.

So how to make it writable?

Update

// global.d.ts 
import * as io from "socket.io";

declare global {
  let server_socket: io.Server
  let user_socket: io.Socket
}

// server.ts
import * as io from "socket.io";

console.log(server_socket)

回答1:

In TypeScript, declare blocks are used to describe your global variables. In other words, they are a way of telling TypeScript what it can expect in the global namespace — but it's your responsibility as a developer to make sure they are actually there.

The way you can create (and describe) global variables depends on the platform.

The browser (DOM)

import * as io from 'socket.io';

window.SocketServer = io.default();

declare global {
  interface Window {
    SocketServer: io.Server;
  }
}

Requires @types/socket.io. Is consumed by accessing window.SocketServer.

Node.js

import * as io from 'socket.io';

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

global.SocketServer = io.default();

Requires @types/socket.io and @types/node. Is consumed by accessing global.SocketServer.

Universal

You can also describe a variable that is already a part of your environment and is accessible to both the client and the server.

An example of such a variable would be process — it's a part of Node.js environment, but build tools like Webpack can expose its contents to the client.

import * as io from 'socket.io';

declare global {
  var SocketServer: io.Server;
}

来源：https://stackoverflow.com/questions/53897466/how-to-create-writable-global-variable-in-node-js-typescript

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typescript

variables

global