Load an HTML Page (in same tab) stored within same folder by Javascript

So there are html pages, 'login.html' and 'register.html' stored within same folder on my desktop.

when i open my login.html page it has a button when clicked should be redirected to register.html page.

i have checked that the button event it self is working fine when button is pressed the event is fired (confirmed through alert method)

    document.getElementById('logIn').onclick= function(){
    window.location.href("login.html") // does not works 
    window.location.href("./login.html") // does not works 
    window.location.href("/login.html") // does not works 
    window.location ="login.html" // does not works 
    window.open("login.html")// open it but in a new tab (which i dont want)
    window.open("login.html","_self")// does not works 
}

also i am not using jquery for this project.