Definitelytyped: @types/ws isAlive missing?

[nihiluis]

it seems isAlive property is missing from WebSocket type. see this: https://github.com/websockets/ws#how-to-detect-and-close-broken-connections

[danthegoodman]

The isAlive property is being dynamically added to the ws instance in the listed example. That property isn't provided by the library.

[Spongman]

how does one add this property to the WebSocket declaration?

I have tried all sorts of things to get this to work.

import express from 'express';
import expressWS from 'express-ws';
import WebSocket from 'ws';

declare global {
  class WebSocket {
    isAlive: boolean;
  }
}

doesn't work. how is this supposed to work?

[danthegoodman]

@Spongman Instead of declaring it globally, try this:

declare module "ws" {
  interface WebSocket {
    isAlive: boolean;
  }
}

You can read more about it here: https://www.typescriptlang.org/docs/handbook/declaration-merging.html#module-augmentation

[DISKONEKTeD]

All you have to do is declare this in your file:

interface ExtWebSocket extends WebSocket {
    isAlive: boolean;
}

then wherever you're defining that, for example:

setInterval(() => {
    wss.clients.forEach((ws: WebSocket) => {
        const extWs = ws as ExtWebSocket;

        if (!extWs.isAlive) return ws.terminate();

        extWs.isAlive = false;
        ws.ping(null, undefined);
    });
}, 10000);

You cannot augment it via a module, as this particular library implements it using a class and not an interface.

This uses type assertion: https://basarat.gitbooks.io/typescript/docs/types/type-assertion.html