const fileField = document.querySelector('input[type="file"]'); fileField.addEventListener("change",() => { console.log(fileField.files[0]); }); document.getElementById("id_run").addEventListener("click", function(e){ alert("Run script"); startBackgroundScript(); e.preventDefault(); }); function startBackgroundScript() { browser.runtime.sendMessage({state : "Button_clicked", fileHandler:fileField); console.log("home.js sent button_clicked message..."); }