background.js

/**
 * @author Atef Ben Ali
 */
// Called when the user clicks on the browser action.
chrome.browserAction.onClicked.addListener(function() {
  // No tabs or host permissions needed!
  chrome.tabs.executeScript({
    code:
      'if(document.getElementsByClassName("CodeMirror-lines")[0]) {' +
      'document.getElementsByClassName("CodeMirror-lines")[0].setAttribute("style", "direction: rtl");' +
      "}" +
      'if(document.getElementById("readme")) {' +
      'document.getElementById("readme").setAttribute("style", "direction: rtl");' +
      "}" +
      'if(document.querySelectorAll("table[data-tab-size]").length) {' +
      'document.querySelectorAll("table[data-tab-size]").forEach((el) => {' +
      'el.setAttribute("style", "direction: rtl")' +
      "});" +
      "}"
  });
});