If you'd like to use Subresource Integrity in your <script ...>
tag, to generate the string for a particular JS file:
curl FULL_URL_TO_JS_FILE | openssl dgst -sha384 -binary | openssl base64 -A
For example:
curl https://unpkg.com/esri-leaflet-cluster@2.1.0/dist/esri-leaflet-cluster.js | openssl dgst -sha384 -binary | openssl base64 -A