how to control back button event in Jquery mobile?

Recommended method pagecontainerbeforechange: https://jqmtricks.wordpress.com/2014/12/01/detect-back-navigation/

You need to listen to navigation event and state.direction.

$(window).on("navigate", function (event, data) {
  var direction = data.state.direction;
  if (direction == 'back') {
    // do something
  }
  if (direction == 'forward') {
    // do something else
  }
});

jQM API: Navigation event

Demo

You can do this without Jquery mobile

window.addEventListener("hashchange", function(e) {
    if(e.oldURL.length > e.newURL.length)
        alert("back")
});

<a href="#p2">goto page 2</a> and then use browser's navigation.</div>

And also Demo in codepen