Ajax with history.pushState and popstate - what do I do when popstate state property is null?

Question

I\'m trying out the HTML5 history API with ajax loading of content.

I\'ve got a bunch of test pages connected by relative links. I have this JS, which handles clicks on

Answer 1

I still don't understand why the back button behaves like this - I'd have thought the browser would be happy to step back to an entry that was created by a normal request. Maybe when you insert other entries with pushState the history stops behaving in the normal way. But I found a way to make my code work better. You can't always depend on the state property containing the URL you want to step back to. But stepping back through history changes the URL in the address bar as you would expect, so it may be more reliable to load your content based on window.location. Following this great example I've changed my popstate handler so it loads content based on the URL in the address bar instead of looking for a URL in the state property.

One thing you have to watch out for is that some browsers (like Chrome) fire a popstate event when you initially hit a page. When this happens you're liable to reload your initial page's content unnecessarily. So I've added some bits of code from the excellent pjax to ignore that initial pop.

$(document).ready(function(){

    // Used to detect initial (useless) popstate.
    // If history.state exists, pushState() has created the current entry so we can
    // assume browser isn't going to fire initial popstate
    var popped = ('state' in window.history && window.history.state !== null), initialURL = location.href;

    var content = $('#content');

    var ajaxLoadPage = function (url) {

        console.log('Loading ' + url + ' fragment');
        content.load(url + '?fragment=true');

    }

    // Handle click event of all links with href not starting with http, https or #
    $('a').not('[href^=http], [href^=https], [href^=#]').on('click', function(e){

        e.preventDefault();
        var href = $(this).attr('href');
        ajaxLoadPage(href);
        history.pushState({page:href}, null, href);

    });

    $(window).bind('popstate', function(event){

        // Ignore inital popstate that some browsers fire on page load
        var initialPop = !popped && location.href == initialURL;
        popped = true;
        if (initialPop) return;

        console.log('Popstate');

        // By the time popstate has fired, location.pathname has been changed
        ajaxLoadPage(location.pathname);

    });

});

One improvement you could make to this JS is only to attach the click event handler if the browser supports the history API.