2.2.1. Target block instances and retrieve attributes

target-frontend-blocks.js

const trackerClass = 'wp-block-rave-initiative-tracker';
const trackers     = document.querySelectorAll( `.${trackerClass}` );

trackers.forEach( ( tracker ) => {
    const attributes = {
        block_id: tracker.dataset.id,
        post_id: parseInt( tracker.dataset.post_id, 10 ),
    };
} );