WordPress at a glance
function is not described

build_dropdown_script_block_core_categories() WP 1.0

Generates the inline script for a categories dropdown field.

No Hooks.

Return

String. Returns the dropdown onChange redirection script.

Usage

build_dropdown_script_block_core_categories( $dropdown_id );
$dropdown_id(string) (required)
ID of the dropdown field.

Code of build dropdown script block core categories: wp-includes/blocks/categories.php VER 5.1.1

<?php
function build_dropdown_script_block_core_categories( $dropdown_id ) {
	ob_start();
	?>
	<script type='text/javascript'>
	/* <![CDATA[ */
	( function() {
		var dropdown = document.getElementById( '<?php echo esc_js( $dropdown_id ); ?>' );
		function onCatChange() {
			if ( dropdown.options[ dropdown.selectedIndex ].value > 0 ) {
				location.href = "<?php echo home_url(); ?>/?cat=" + dropdown.options[ dropdown.selectedIndex ].value;
			}
		}
		dropdown.onchange = onCatChange;
	})();
	/* ]]> */
	</script>
	<?php
	return ob_get_clean();
}