https://randpaul.com/wp-content/plugins/meta-box/js/autosave.js

1( function ( $, document ) {
2	'use strict';
3
4	$( document ).ajaxSend( function ( event, xhr, settings ) {
5		if ( ! Array.isArray( settings.data ) || -1 === settings.data.indexOf( 'wp_autosave' ) ) {
6			return;
7		}
8		var inputSelectors = 'input[class*="rwmb"], textarea[class*="rwmb"], select[class*="rwmb"], button[class*="rwmb"], input[name^="nonce_"]';
9		$( '.rwmb-meta-box' ).each( function () {
10			var $meta_box = $( this );
11			if ( true === $meta_box.data( 'autosave' ) ) {
12				settings.data += '&' + $meta_box.find( inputSelectors ).serialize();
13			}
14		} );
15	} );
16} )( jQuery, document );