<script src="https://unpkg.com/hs2js@0.0.3"></script>
<button id="hello">hello</button>
<script>
  hs2js.setBase('https://unpkg.com/hs2js@0.0.3/dist/');
  hs2js.loadParser();
  document.getElementById('hello').addEventListener('click', () => {
    hs2js.evaluate('alert "hello from haskell!"');
  });
</script>

Via npm

You need to add postinstall to your package.json script to copy the parser to your public folder:

{
  "scripts": {
    "postinstall": "cp node_modules/hs2js/dist/tree-sitter.wasm public && cp node_modules/hs2js/dist/tree-sitter-haskell.wasm public"
  }
}

Depending on your setup, replace public with the folder that will serve your assets to /. Then install the package:

npm i hs2js

and use it:

import * as hs2js from 'hs2js';
hs2js.loadParser();
document.getElementById('hello').addEventListener('click', () => {
  hs2js.evaluate('alert "hello from haskell!"');
});