Greasemonkey Userscript to set the C++ standard on cppreference.com

greasemonkey_cppreference_setCppStandard.js

// ==UserScript==
// @name     Set C++ standard on cppreference.com
// @match    https://en.cppreference.com/w/cpp/*
// @icon     https://en.cppreference.com/favicon.ico
// ==/UserScript==

const DESIRED_CPP_STANDARD = "C++20";

function changeCppStandard(elem) {
  // find option labeled with DESIRED_CPP_STANDARD
  let desired_value = "";
  for (const option of elem.options) {
    if (option.text === DESIRED_CPP_STANDARD) {
      desired_value = option.value;
      break;
    }
  }
  if (desired_value === "") {
    console.warn(
      '[userscript] no standard option labeled "' +
        DESIRED_CPP_STANDARD +
        '" found'
    );
    return;
  }

  // set value, dispatch change event
  elem.value = desired_value;
  elem.dispatchEvent(new Event("change"));
  console.info("[userscript] standard set to " + DESIRED_CPP_STANDARD);
}

// define observer callback
const callback = (mutations, observer) => {
  for (const mutation of mutations) {
    if (mutation.type === "childList") {
      // search added children for <select> element
      for (const node of mutation.addedNodes) {
        if (node.nodeType === Node.ELEMENT_NODE) {
          if (node.className === "stdrev-select") {
            const selectElem = node.querySelector("select");
            // change C++ standard and discontinue observing
            changeCppStandard(selectElem);
            observer.disconnect();
          }
        }
      }
    }
  }
};

// start observing the toolbar
const toolbar = document.querySelector("#cpp-head-tools-right");
const observer = new MutationObserver(callback);
observer.observe(toolbar, { childList: true });