history pushState and scroll position

Question

I am trying to retrieve the scroll position when a user navigates back in the browser history using HTML5 popstate handler.

Here is what I have:

$(document).ready(function () {

    $(window).on('popstate', PopStateHandler);

    $('#link').click(function (e) {

        var stateData = {
            path: window.location.href,
            scrollTop: $(window).scrollTop()
        };
        window.history.pushState(stateData, 'title', 'page2.html');
        e.preventDefault();

    });

});

function PopStateHandler(e) {
    alert('pop state fired');
    var stateData = e.originalEvent.state;
    if (stateData) {
        //Get values:
        alert('path: ' + stateData.path);
        alert('scrollTop: ' + stateData.scrollTop);
    }
}


<a id="link" href="page2.html"></a>

When I navigate back, I am unable to retrieve the values of the stateData.

I presume this is because the popstate is retrieving the values of the initial page load and not the state I pushed to the history when the hyperlink was clicked.

How could I go about getting the scroll position on navigating back?

Answer 1

I managed to solve this one myself:

We must overwrite the current page on the history stack before navigating to the new page.

This allows us to store the scroll position and then pop it off the stack when we navigate back:

    $('#link').click(function (e) {

        //overwrite current entry in history to store the scroll position:
        stateData = {
            path: window.location.href,
            scrollTop: $(window).scrollTop()
        };
        window.history.replaceState(stateData, 'title', 'page2.html');

        //load new page:
        stateData = {
            path: window.location.href,
            scrollTop: 0
        };
        window.history.pushState(stateData, 'title', 'page2.html');
        e.preventDefault();

    });