ServiceNow：コールバック関数でonSubmitを呼び出すと、無限ループが発生します

あなたのonSubmit()関数は常に返すfalseためにmifi要求。onSubmit（）関数は、を返すときに、より安全な送信を実行できtrueます。また、g_formコールバック関数はサーバー上で実行されるため、関数を実行することはできません。

関数g_form.submit()の最後にを付けるのではなく、関数にを返します。checkDateDiffonSubmit()true

このようなものが機能するはずです。変更したすべての行にコメントしました。

function onSubmit() {
    var requestType = g_form.getValue('request_type');
    if (requestType == 'mifi') {
        console.log("calling validateTravelEndDate()");

        // **CHANGED CODE: instead of g_form.submit(), this will return true
        if(validateTravelEndDate()){
            return true;
        }
        else{
            return false;
        }

    } else
        return true;
}

//Helper function which calls a AJAX script include called "ClientDateTimeUtils" which gives the response in a callback where i am deciding whether to submit the form or not based on the status of days result.

function validateTravelEndDate() {
    var startDate = g_form.getValue('travel_start'); //First Date/Time field
    var endDate = g_form.getValue('travel_end'); //Second Date/Time field
    var dttype = 'day'; //this can be day, hour, minute, second. By default it will return seconds.
    console.log("startDate :" + startDate + "endDate :" + endDate);
    var ajax = new GlideAjax('ClientDateTimeUtils'); // This is the script include which can be used for date validation.
    ajax.addParam('sysparm_name', 'getDateTimeDiff');
    ajax.addParam('sysparm_fdt', startDate);
    ajax.addParam('sysparm_sdt', endDate);
    ajax.addParam('sysparm_difftype', dttype);
    console.log("before " + g_form.getValue('travel_end'));

    // **CHANGED CODE: validateTravelEndDate returns the callback value
    return ajax.getXML(checkDateDiff);
}

// callback function where deciding to go ahead or not with form submission.
function checkDateDiff(response) {
    var answer = response.responseXML.documentElement.getAttribute("answer");
    console.log("difference in days:" + answer);
    if (answer <= 0) {
        alert("Travel End date must be after Travel Start date.");
        g_form.setValue('travel_end', '');
        g_form.showFieldMsg('travel_end', 'Please provide a future date', 'error');
        return false;
    }
    else {
    // **CHANGED CODE: checkDateDiff will return true
        return true;
    }
}