Retrieving Post Meta Value in the Gutenberg Block Editor : https://jeffreycarandang.com/how-to-enable-read-and-update-post-meta-in-the-wordpress-block-editor-gutenberg/(opens in a new tab)

read_meta.js

import { useSelect } from '@wordpress/data';

/**
 * My Custom Block
 */
const MyCustomBlock = () => {
    const META_KEY = 'custom_post_meta';
    const meta = useSelect((select) =>
        select('core/editor').getEditedPostAttribute('meta')
    );
    const { [META_KEY]: customMeta } = meta;

    console.log(customMeta); // Log the value into the browser console.

    return null; // Return your block content here.
};