bg.js

/*******************************************************************************
    Measure=it - A browser extension to measure parts of page.
    Copyright (C) 2017-2019 Trishul Goel

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see {http://www.gnu.org/licenses/}.

    Home: https://github.com/tsl143/measure-it
*******************************************************************************/

localStore.get('choices')
.then((res = {}) => {
  const {choices = {}} = res;
  choices.background = choices.background || '#000000';
  choices.popup = choices.popup || '#ffff00';
  choices.popupOpacity = choices.popupOpacity || '0.3';
  choices.backgroundOpacity = choices.backgroundOpacity || '0.4';
  localStore.set({choices});
});

const execCs = tabId => {
  localStore.get('choices')
  .then((res = {}) => {
    const {choices} = res;
    chrome.tabs.executeScript(tabId, {code: `measureitChoices = '${JSON.stringify(choices)}';`});
    chrome.tabs.executeScript(tabId, {file: 'cs.js'});
  });
}

chrome.browserAction.onClicked.addListener(tab => {
  execCs(tab.Id);
});