import browser from 'webextension-polyfill'; browser.runtime.onMessage.addListener((message: any) => { console.log('HELLO MESSAGE', message); if (message.action === 'insertFolkCanvas') { // Inject 'injected.js' into the page context const script = document.createElement('script'); script.src = browser.runtime.getURL('injected.js'); script.onload = function () { script.remove(); }; (document.head || document.documentElement).appendChild(script); } return true; });