@wordpress/block-editor/src/utils/selection.js

Generic block editor.

/**
 * A robust way to retain selection position through various
 * transforms is to insert a special character at the position and
 * then recover it.
 */
export const START_OF_SELECTED_AREA = '\u0086';

/**
 * Retrieve the block attribute that contains the selection position.
 *
 * @param {Object} blockAttributes Block attributes.
 * @return {string|void} The name of the block attribute that was previously selected.
 */
export function retrieveSelectedAttribute( blockAttributes ) {
	if ( ! blockAttributes ) {
		return;
	}

	return Object.keys( blockAttributes ).find( ( name ) => {
		const value = blockAttributes[ name ];
		return (
			typeof value === 'string' &&
			value.indexOf( START_OF_SELECTED_AREA ) !== -1
		);
	} );
}