这里有什么交易？

JS函数的自定义。js\'

function validate() {
    var email = jQuery("#billingemail").val();

    if (isValidEmailAddress(email)) {
        jQuery.ajax({
            type: \'POST\',
            url: ajaxurl,
            data: {"action": "custome_ajax_email_check", "guestemail": email },
            success: function(data){
                data = jQuery.parseJSON(data);
                if(data.result) {
                    alert(\'Email Exists\');
                    return false;
                } else {
                    alert(\'Email Does Exists\');
                    return true;
                }
            }
        });
    } else {
        return false;
    }
}

点击“自定义”。js\'

 $(\'#mwb_logincoupon\').on(\'click\', \'#validateguestemail\', function (e) {
        e.preventDefault();
        validateemail = validate();
        

PHP AJAX

add_action( \'wp_ajax_custome_ajax_email_check\', \'custome_ajax_email_check\' );
add_action(\'wp_ajax_nopriv_custome_ajax_email_check\', \'custome_ajax_email_check\');

function custome_ajax_email_check(){
    $email = $_POST[\'guestemail\'];

    // do check
    if ( email_exists($email) ) {
        $response->result = true;
    }
    else {
        $response->result = false;
    }

    echo( json_encode( $response));
    wp_die();
}

调试JS代码进入的脚本success 功能，甚至触发alert(\'Email Exists\').. 但是return 函数中的语句从未检索到，因此validateemail 始终返回undefined. 为什么？

async function doAjax(email) {
    let result;

    try {
        result = await jQuery.ajax({
            url: ajaxurl,
            type: \'POST\',
            data: {"action": "custome_ajax_email_check", "guestemail": email }
        });

        return result;
    } catch (error) {
        console.error(error);
    }
}

function validate() {
    var email = jQuery("#billingemail").val();

    if (isValidEmailAddress(email)) {
        doAjax(email).then( (data) => ajaxCallResult(data) )
    }

  . . . . . 

function ajaxCallResult(data){

    data = jQuery.parseJSON(data);
 
  . . . . . .