Function triggerOnceWhenElementExists. It creates jQuery listeners which will trigger the code on a specific event eventName once only if the element exists

jquery-trigger-once.js

function generateRandomIdentifier(length) {
    const firstLetterCode = 97;
    const numberOfLetters = 25;

    const randomCharacter = function () {
        const letterPosition = Math.round(numberOfLetters * Math.random());
        return String.fromCharCode(firstLetterCode + letterPosition);
    };

    let identifier = '';

    for (let i = 0; i < length; i += 1) {
        identifier += randomCharacter();
    }

    return identifier;
}

function triggerOnceWhenElementExists(eventName, elementSelector, callback) {
    // 12 letters should be enough in order not to create collision of
    // coexisting custom events
    const customEventName = generateRandomIdentifier(12);

    const triggerHandler = function () {
        if ($(elementSelector).length > 0) {
            $(document).trigger(customEventName);
        }
    };

    $(document).on(eventName, triggerHandler);

    // Trigger only once
    $(document).one(customEventName, function () {
        callback();

        // Unbind the existing listener, since it's not needed anymore
        $(document).off(eventName, triggerHandler);
    });
}