amazon_url.userscript.js

// ==UserScript==
// @name         Amazon Enhanced URL Processor
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Processes Amazon URLs for various enhancements.
// @author       ChatGPT with assistance from a1678991
// @match        https://www.amazon.co.jp/*
// @grant        none
// @run-at       document-start
// ==/UserScript==

(function () {
  "use strict";

  /**
   * @param {URL} url
   */
  function processSearchPage(url) {
    if (url.pathname.startsWith("/s") && !url.searchParams.has("emi")) {
      url.searchParams.set("emi", "AN1VRQENFRJN5");
    }
  }

  /**
   * @param {URL} url
   */
  function simplifyProductURL(url) {
    const asinMatch = url.pathname.match(/\/(dp|gp\/product)\/([A-Z0-9]{10})/);
    if (asinMatch && asinMatch[2] && asinMatch[2].length === 10) {
      url.pathname = `/dp/${asinMatch[2]}`;
      url.search = "";
    }
  }

  /**
   * @param {URL} url
   * @param {string[]} params
   */
  function removeParameters(url, params) {
    params.forEach((param) => url.searchParams.delete(param));
  }

  function updateUrl() {
    /** @type {URL} */
    let currentUrl = new URL(window.location.href);
    /** @type {string} */
    let originalUrlString = currentUrl.toString();

    processSearchPage(currentUrl);
    simplifyProductURL(currentUrl);
    removeParameters(currentUrl, [
      "ref",
      "ref_",
      "pf_rd_p",
      "pf_rd_r",
      "pd_rd_wg",
      "pd_rd_r",
      "pd_rd_w",
    ]);

    if (originalUrlString !== currentUrl.toString()) {
      window.location.href = currentUrl.toString();
    }
  }

  updateUrl();
})();