var scanCodeButton = document.getElementById('scanCode') var modifyPwdButton = document.getElementById('modifyPwd') var container = document.getElementById('middle-container') if (scanCodeButton !== null) { scanCodeButton.addEventListener('click', function () { container.classList.add('right-panel-active') }) } if (modifyPwdButton !== null) { modifyPwdButton.addEventListener('click', function () { container.classList.remove('right-panel-active') }); }