<namespace path="src">Am\Module\Amap</namespace>
   ...

Joomla.request({
	url: "index.php?option=com_ajax&module=amap&method=getReloadLayoutParams&format=json",
	method: "POST",
	headers: {
		"Cache-Control" : "no-cache",
		"Content-Type" : "application/json"
	},
	onBefore: function (xhr){
		console.log("onBefore");
	},

	onSuccess: function (response, xhr){
		if (response !== ""){
			let res = JSON.parse(response);
			console.log(res.message);
		}
		console.log("onSuccess");
	},
					
        onError: function(xhr){
		console.log("onError");
	},

	onComplete: function (xhr){
		console.log("onComplete");
	}
});

<?php
namespace Am\Module\AMAP\Site\Helper;

\defined( '_JEXEC' ) or die;

class AmapHelper
{
        public static function getReloadLayoutParamsAjax()
	{
		$html = array();
		$html['success'] = true;
		$html['message'] = 'Ok';
		$html['messages'] = '';
		$html['data'] = array();
		
		echo json_encode($html);
                exit;
	}
}

onBefore
File mod_amap/helper.php does not exist. // ??? It doesn't exist anyway
onSuccess
onComplete