With https://github.com/substack/node-browserify you can work with buffers in the Browser by using: https://github.com/toots/buffer-browserify. However: this can be very slow in the browser: For faster access use https://github.com/chrisdickinson/bops

These instructions worked for me. Cheers!

Here are the instructions you can look at the web section. https://github.com/feross/buffer

Here is what the instructions state about using it in the browser without browserify. So from what you tried

 browserify test.js -o buffer.js

I would just use the version directly that does not require browserify

To use this module directly (without browserify), install it:

npm install buffer

To depend on this module explicitly (without browserify), require it like this:

var Buffer = require('buffer/').Buffer // note: the trailing slash is important!

The Buffer object is only available in NodeJs and does not exist in the browser JS. But there is a script available that can be used available on GitHub.

Add standalone script to HTML from https://github.com/feross/buffer

    <script src="https://bundle.run/buffer@6.0.3"></script>

Then in JS

const privateKey = buffer.Buffer.from(PRIVATE_KEY_1, "hex");