Cause back button to close Bootstrap modal windows

backbutton-closebootstrap-modal.js

// For the below to work with the escape key
// I needed to add data-keyboard="false" to the modal
// in the HTML so that the standard bootstrap function
// doesn't fire, the below fires instead

$('div.modal').on('show.bs.modal', function() {
    var modal = this;
    var hash = modal.id;
    window.location.hash = hash;
    window.onhashchange = function() {
        if (!location.hash){
            $(modal).modal('hide');
        }
    }
});

$('div.modal').on('hidden.bs.modal', function() {
    var hash = this.id;
    history.replaceState('', document.title, window.location.pathname);
});

// when close button clicked simulate back
$('div.modal button.close').on('click', function(){
    window.history.back();
})

// when esc pressed when modal open simulate back
$('div.modal').keyup(function(e) {
    if (e.keyCode == 27){
        window.history.back();          
    }
});

Works great, thanks!
My only problem was that clicks next to the modal closed it, but did not clear the history entry, so I had to click through several empty history entries.
My solution was to listen to the hide.bs.modal-event (instead of the different close-triggers individually) and using history.back() if the hash-fragment is still there (user did not use back button, but close icon, overlay, etc).
Might be helpful to someone else:

$('div.modal').on('show.bs.modal', function() {
  var modal = this;
  var hash = modal.id;
  window.location.hash = hash;
  window.onhashchange = function() {
      if (!location.hash) {
          $(modal).modal('hide');
      }
  }
});

$('div.modal').on('hide.bs.modal', function(e) {
  // hash fragment is still there? User did not use back-button, reset browser history manually now
  // check referrer to disable this for links that where copied and opened with the hash
  if (location.hash && document.referrer.includes(location.host)) {
    window.history.back();
  } 
});

edit: Added a referrer-check