如何使用正確的控制項在 AJAX 驅動的網站上自動執行任務？

// ==UserScript==
// @name     Nike Shoe Auto-Purchase
// @include  http://*nike.com/*
// @require  http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js
// @require  https://gist.github.com/raw/2625891/waitForKeyElements.js
// ==/UserScript==

const targetShoeSize = "10";

waitForKeyElements(
  "span.sizeDropdown a.size-dropdown",
  activateSizeDropdown
);

function activateSizeDropdown(jNode) {
  jNode.trigger("mousedown");

  waitForKeyElements(
    "li a:contains('" + targetShoeSize + "')",
    selectDesiredShoeSize
  );
}

function selectDesiredShoeSize(jNode) {
  jNode.trigger("click");

  waitForKeyElements(
    "span.selectBox-label:contains('(" + targetShoeSize + ")')",
    addItemToCart
  );
}

function addItemToCart(jNode) {
  $("div.add-to-cart").trigger("click");

  waitForKeyElements("a.checkout-button", clickCheckout);
}

function clickCheckout(jNode) {
  jNode.trigger("click");
}