[Chrome拡張] 表示しているページのタイトルとURLをmarkdown形式でクリップボードへコピー

manifest.json

{
  "manifest_version": 2,
  "name": "markdown_url",
  "version": "1.0.0",

  "description": "format the page link as markdown",

  "background": {
    "scripts": ["script.js"],
    "persistent": false
  },

  "permissions": [
    "clipboardRead",
    "contextMenus",
    "tabs"
  ]
}

script.js

// 参考
// https://qiita.com/MugeSo/items/e5307bda346c0bb8e22e
// http://zentoo.hatenablog.com/entry/2014/01/26/200914

const ContextMenus = new function () {
  let items = {};
  let callbacks = {};

  this.setItems = function (aItems) {
      aItems.forEach(function (item) {
          callbacks[item.id] = item.onclick;
          item.onclick = null;
          items[item.id] = item;
      });
  };

  this.create = function () {
      Object.keys(items).forEach(
          function (key) {
              chrome.contextMenus.create(items[key]);
          }
      );
  };

  chrome.contextMenus.onClicked.addListener(function (info, tab) {
      callbacks[info.menuItemId](info, tab);
  });
};

ContextMenus.setItems([
  {
    type: 'normal',
    id: 'copy_pageUrl',
    title: "[md]このページのurlをコピー",
    onclick: copyPageUrl
  }
]);

chrome.runtime.onInstalled.addListener(ContextMenus.create);

function copyPageUrl(info, tab) {
  let title = tab.title
  let url = tab.url

  if(title !== '' && url !== '')
    saveToClipboad(`[${title}](${url})`)
}

function saveToClipboad(str) {
  var textArea = document.createElement("textarea");
  textArea.style.cssText = "position:absolute;left:-100%";

  document.body.appendChild(textArea);

  textArea.value = str;
  textArea.select();
  document.execCommand("copy");

  document.body.removeChild(textArea);
}