jet-engine-rank-math-checkboxes.php

<?php
add_action( 'admin_footer', function() {
?>
<script>
	class JetEngineCheckboxSEO {

		constructor() {

			if ( ! window.rankMathEditor ) {
				return;
			}
			
			let self = this;
			
			jQuery( document ).on( 'input change', '.cx-checkbox-input', () => {
				window.rankMathEditor.refresh( 'content' );
			} );
			
			wp.hooks.addFilter( 'rank_math_content', 'jet-engine-checkbox-seo', ( content ) => {
				
				jQuery( '.cx-control-checkbox' ).each( ( groupIndex, groupEl ) => {
					
					let $grEl = jQuery( groupEl );
					let selectedItems = [];
					
					$grEl.find( 'input[checked]' ).each( ( itemIndex, itemEl ) => {
						selectedItems.push( jQuery( itemEl ).siblings( '.cx-checkbox-label' ).text() );
					} );
										
					if ( selectedItems.length ) {
						content += '\n' + $grEl.find( '.cx-control__title' ).text() + ': ' + selectedItems.join( ", " );
					}
				} );
								
				return content;
			} );
		}

		getContent( content ) {
			return content;
		}
	}
	
	window.addEventListener( "load", ( event ) => {
		new JetEngineCheckboxSEO();
	} );
</script>
<?php
}, 999 );