Have the Modal show

My modal only needs to show once when you open the browser page, not pop up every time you go back to that page. When you close the website and open it up again, it has to display again.....

let current_location = window.location.pathname;

let session_variable = sessionStorage.getItem(current_location);

if(session_variable) {
    console.log("Exists");
} else {
    console.log("Empty");
    sessionStorage.setItem(current_location, "Modal");
}