# Testing js lib on production

To troubleshoot some issue with websocket connection on production, I need to test the library ([reconnecting-websocket][1]) that we use to manage the connection.

I want to do some testing in dev console. The problem is that the library is not available in the global scope. And we can't simply import it from the dev console.

![Screenshot from 2020-11-28 17-45-13.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1606556753848/fDrx7gdyY.png)

Thanks to [this article][2], it has detailed approaches on how to solve this. <s>I decided to use the `eval()` method - be sure to read the caveat on the security issue though</s>.

There's no need to use `eval()` actually. Since we're loading external script through `src` attribute, that will be immediately executed when we use `.appendChild()`.

Enter this code through the dev console:-

```
const script = document.createElement('script')
script.type = "text/javascript"
script.src='https://cdnjs.cloudflare.com/ajax/libs/reconnecting-websocket/1.0.0/reconnecting-websocket.js'
document.head.appendChild(script)
eval(script)
ws_connection = new ReconnectingWebSocket("wss://oursite.com/ws/xxx/");
ws_connection.onmessage = function (e) {let data = JSON.parse(e.data);console.log("socket_dataxf", data);}
```

![Screenshot from 2020-11-26 11-57-40.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1606557393186/MnotK26en.png)

Simple snippet above allow me to start receiving data from server and help in my troubleshooting.

[1]:https://www.npmjs.com/package/reconnecting-websocket
[2]:https://levelup.gitconnected.com/how-to-load-external-javascript-files-from-the-browser-console-8eb97f7db778