FindInWindows.js

window.addEventListener("DOMContentLoaded", () => {
  const highlightResults = (text, color) => {
    document.designMode = "on"; // https://stackoverflow.com/a/5887719
    var selection = window.getSelection();
    selection.collapse(document.body, 0);
    while (window.find(text)) {
      document.execCommand("HiliteColor", false, color);
      selection.collapseToEnd();
    }
    document.designMode = "off";
  };

  let mostRecentSearchText = "";
  const search = text => {
    highlightResults(mostRecentSearchText, "transparent");
    highlightResults(text, "rgb(255 255 1 / 50%)");
    mostRecentSearchText = text;
  };

  const input = document.createElement("input");
  input.placeholder = "Search...";
  input.style.padding = "10px 15px";
  input.style.fontSize = "15px";
  input.style.borderRadius = "3px";
  input.style.border = "solid 1px lightgray";

  const form = document.createElement("form");
  form.style.display = "none";
  form.style.position = "fixed";
  form.style.top = "15px";
  form.style.right = "15px";
  form.style.zIndex = "2147483647"; // https://stackoverflow.com/a/856569
  form.addEventListener("submit", e => {
    e.preventDefault();
    search(input.value);
  });

  const close = document.createElement("a");
  close.innerText = "⨯";
  close.href = "javascript:void(0)";
  close.style.fontSize = "30px";
  close.style.padding = "15px";
  close.style.textDecoration = "none";
  close.addEventListener("click", e => {
    e.preventDefault();
    search("");
    form.style.display = "none";
  });

  form.appendChild(input);
  form.appendChild(close);
  document.body.appendChild(form);

  document.addEventListener("keydown", event => {
    if (event.metaKey && event.key === "f") {
      event.preventDefault();
      form.style.display = "block";
      input.focus();
    }
  });
});