Horizontal Scrollable Tab with Localstorage to Remember Tab Last Opened

Hi. I am using a horizontal scrollable tabs at https://www.littlechinesereaders.com/courses/level-1-lessons/ and vertical tabs at https://www.littlechinesereaders.com/guided-courses/ with the following javascript in the GP footer hook. I'd like to have a way of remembering the user's last visited tab (perhaps using localstorage) so that the same tab will load when the user revisits the page. How do I do that?

function openCity(evt, cityName) {
var i, tabcontent, tablinks;
tabcontent = document.getElementsByClassName("tabcontent");
for (i = 0; i < tabcontent.length; i++) {
tabcontent[i].style.display = "none";
}
tablinks = document.getElementsByClassName("tablinks");
for (i = 0; i < tablinks.length; i++) {
tablinks[i].className = tablinks[i].className.replace(" active", "");
}
document.getElementById(cityName).style.display = "block";
evt.currentTarget.className += " active";
}
document.getElementById("defaultOpen").click();