HTML5 History API back button with partial page loads

Question

To improve the performance/responsiveness of my website I have implemented a partial page load using AJAX, replaceState, pushState, and a popstate listener.

I essentially store the central part of my page (HTML) as my state object in the history. When a link is clicked I request just the central bit of the page from the server (identifying these requests with a different Accept header) and replace it with javascript. On popstate I grab the previous central part and push it back into the dom.

This mostly works fine, however I have found a particular issue which I am stuck on. It is a little complicated to explain, so my apologies if this isn't very clear.

There is a search form on most of our pages. The partial page loading via ajax is only on GET requests, and the form performs a POST which results in a full page load.

If I navigate the following set of pages, I end up on a malformed partial page consisting of ONLY the central content, without any of the surrounding dom:

Start on the Home Page (via full page load) - perform a Search (post-redirect-get)
Takes you to Search Results (via full page load) - then click Home
Returns you to the Home Page (via dynamic get) - click browser back
Search Results (from popstate listener) - click browser back
Malformed home page.

When the malformed home page appears, my popstate listener is not present at all.

What I think is happening, is that the second load (dynamic, partial) of the home page is being cached by the browser, and then when the full page back occurs, the browser is merely showing the cached partial response rather than the full page.

To try to remedy this I have added a Vary: Accept header to the response to let the browsers know that content may change based on the accept header. I have also added Cache-Control max-age=0, pragma no-cache, and a past expiry date to the partial loaded content to try to force the browser not to cache this, but none of this solves it.

Unfortunately my company does not allow external traffic to our dev servers, so I cannot show you the problem. I have looked at various similar questions on here, but none of them seem quite the same, nor do the solutions suggested seem to work.

If I add a pointless parameter (blah=blah) to my dynamic GET requests, this solves the problem. However this is an ugly hack that I'd rather not do. This seems like it should be solvable with headers, since I think it is a caching problem. Can anyone explain what's going on?

Answer 1

That's a caching issue. With the response header Cache-Control set to no-cache or max-age=0, the problem doesn't happen in FF (as you said), but it persists in Chrome.

The header that worked for me is Cache-Control: no-store. That's not consistently implemented by all the browsers (you can find questions asking what is the difference between no-cache and no-store), but has the result you expect in Chrome as well.

Answer 2

I had a similar issue. I'm building a web-based wizard and using jquery ajax to load each step (ASP.NET MVC on the back end).

The inital route is something like /Questions/Show - which loads the whole page and displays the first question (question 0). When the user clicks the Next image, it does a jquery .load() with the url /Questions/Save/0 . This saves the answer and returns a partial view with the next question. The next save does a jquery .load() with /Questions/Save/1 ...

I implemented History.js so that the user can go back and forward (forth?). It stores the question number in the state data. When it detects a statechange (and the state's question number is different from what's on the page), it does a jquery .load() to load the correct question.

At first I was using the same route as when the initial page is loaded (/Questions/Show/X where X is the question number). On the back end I detected whether it was an ajax request, and if so returned a partial view instead of the full view. This is where the issue came in similar to yours: Say I was on question 3, went back, then forward, then went to www.google.com, and then hit the back button. It showed question 3 but it was the partial view - because the browser cached the partial for that route.

My solution was to create a separate route for the ajax call: /Questions/Load/X (it used common code on the back end). Now with two different routes (/Questions/Show for non-ajax and /Questions/Load for ajax), the browser shows the full page correctly in the above situation.

So maybe a similar solution would work for you... i.e. two different routes for your home page - one for the full page and one for a partial. Hope that helps.

Answer 3

When a link is clicked I request just the central bit of the page from the server (identifying these requests with a different Accept header) and replace it with javascript.

Awesome. That's the RESTful way to do it. But there's one thing left to do to make it work: add a Vary header to the response.

Vary: Accept

That tells the browser that a request with a different Accept header might get a different response. Because the two requests use different Accept headers, the browser (and any caching proxies) will cache the responses separately.

Unlike setting Cache-Control: no-store, this will still allow you to use caching.