Dynamically add a variable to an external js script with NextJS

I have this external hotjar script inside /static/js of my nextjs application.

(function(h,o,t,j,a,r){
        h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)};
        h._hjSettings={hjid:<SITEID>,hjsv:6};
        a=o.getElementsByTagName('head')[0];
        r=o.createElement('script');r.async=1;
        r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv;
        a.appendChild(r);
    })(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv=');

I have imported this file into my app from inside the Head section of _document.js like so: <script src={'/js/hotjar.js'} ></script>

Problem: My Nextjs app is currently running on a staging and live environment and I would like to add a script for both. The only dynamic part of the script above is the SITEID value here h._hjSettings={hjid:<SITEID>,hjsv:6};. How can I add different SITEIDs for different environments inside a config file and dynamically change this value since this script runs on the client side?

Solution

Edit:
you can use react-hotjar and simply

import { hotjar } from 'react-hotjar'; 
hotjar.initialize(hjid, hjsv);// Hotjar ID  and Hotjar Snippet Version

Otherwise You have 2 options:

Option 1
first make sure your package.json start script will set enviroment variable, something like this :

  "scripts": {
    ...
    "start": "cross-env NODE_ENV=production node server.js",
    ...
  }

Then create 2 hotjar sripts, lets say /js/prod_hotjar.js and /js/staging_hotjar.js which have appropriate SITEID inside.
Then in your _document.js detect the current enviroment, and render the appropriate script with something like this :

import Document, { Html, Head, Main, NextScript } from 'next/document'
const prod= process.env.NODE_ENV === 'production'

class MyDocument extends Document {
  static async getInitialProps(ctx) {
    const initialProps = await Document.getInitialProps(ctx)
    return { ...initialProps }
  }

  render() {
    const url = prod ?  "/js/prod_hotjar.js" : "/js/staging_hotjar.js"
    return (
      <Html>
        <Head>
        <script src={url} ></script>
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    )
  }
}

export default MyDocument

Option 2
Use dangerouslySetInnerHTML with something like this :

import Document, { Html, Head, Main, NextScript } from 'next/document'
const dev = process.env.NODE_ENV === 'production'

class MyDocument extends Document {
  static async getInitialProps(ctx) {
    const initialProps = await Document.getInitialProps(ctx)
    return { ...initialProps }
  }

  render() {
    const SITEID = prod ?  1234 :  4567 // or any other logic
    return (
      <Html>
        <Head>
        <script dangerouslySetInnerHTML={{__html: `(function(h,o,t,j,a,r){
        h.hj=h.hj||function(){(h.hj.q=h.hj.q||[]).push(arguments)};
        h._hjSettings={hjid:${SITEID},hjsv:6};
        a=o.getElementsByTagName('head')[0];
        r=o.createElement('script');r.async=1;
        r.src=t+h._hjSettings.hjid+j+h._hjSettings.hjsv;
        a.appendChild(r);
       })(window,document,'https://static.hotjar.com/c/hotjar-','.js?sv=');`}} />
        </Head>
        <body>
          <Main />
          <NextScript />
        </body>
      </Html>
    )
  }
}

export default MyDocument