wp_js_dataset_name( string $html_attribute_name ): string|null

// Dash-letter pairs turn into capital letters.
'postId' === wp_js_dataset_name( 'data-post-id' );
'Before' === wp_js_dataset_name( 'data--before' );
'-One--Two---' === wp_js_dataset_name( 'data---one---two---' );

// Not every attribute name will be interpreted as a custom data attribute.
null === wp_js_dataset_name( 'post-id' );
null === wp_js_dataset_name( 'data' );

// Some very surprising names will; for example, a property whose name is the empty string.
'' === wp_js_dataset_name( 'data-' );
0 === strlen( wp_js_dataset_name( 'data-' ) );
When	Instructions	Calls it makes
always	11	`substr_compare()`
always	20	`substr_compare(), strcspn()`
always	33–41	`substr_compare(), strcspn(), strtolower()`
PHP	Compiled	Executed	Branches	Notes
8.6-dev	74	11–40	10	1 fewer instruction than PHP 8.5
8.5	75	11–41	10
8.4	75	11–41	10	12 fewer instructions than PHP 8.3
8.3	87	11–47	10
8.2	87	11–47	10
8.1	87	11–47	10	1 fewer instruction than PHP 7.4
7.4	88	11–47	10