## pushState + ajax = pjax

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       ."\> \Y/|<'.  '._.-'
      /  \ \_\/ /  '-' /
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          `-"--'---'


## what is it?

pjax loads HTML from your server into the current page
without a full reload. It's ajax with real permalinks,
page titles, and a working back button that fully degrades.

pjax enhances the browsing experience - nothing more.

You can find a demo on <http://pjax.heroku.com/>


## three ways to pjax on the client side:

One. Functionally obtrusive, loading the href with ajax into data-pjax:

```html
<a href='/explore' data-pjax='#main'>Explore</a>
```

```js
$('a[data-pjax]').pjax()
```


Two. Slightly obtrusive, passing a container and binding an error handler:

```html
<a href='/explore' class='js-pjax'>Explore</a>
```

```js
$('.js-pjax').pjax('#main')

$('#main').live('pjax:error', function(e, xhr, err) {
  $('.error').text('Something went wrong: ' + err)
})
```


Three. Unobtrusive, showing a 'loading' spinner:

```html
<div id='main'>
  <div class='loader' style='display:none'><img src='spin.gif'></div>
  <div class='tabs'>
    <a href='/explore'>Explore</a>
    <a href='/help'>Help</a>
  </div>
</div>
```

```js
$('a').pjax('#main').live('click', function(){
  $(this).showLoader()
})
```


## $(link).pjax( container, options )

The `$(link).pjax()` function accepts a container, an options object,
or both. The container MUST be a string selector - this is because we
cannot persist jQuery objects using the History API between page loads.

The options are the same as jQuery's `$.ajax` options with the
following additions:

* `container`      - The String selector of the container to load the
                     reponse body. Must be a String.
* `target`         - The Element that was clicked to start the pjax call.
* `push`           - Whether to pushState the URL. Default: true (of course)
* `replace`        - Whether to replaceState the URL. Default: false
* `timeout`        - pjax sets this low, <1s. Set this higher if using a
                     custom error handler. It's ms, so something like
                     `timeout: 2000`
* `fragment`       - A String selector that specifies a sub-element to
                     be pulled out of the response HTML and inserted
                     into the `container`. Useful if the server always returns
                     full HTML pages.


## $.pjax( options )

You can also just call `$.pjax` directly. It acts much like `$.ajax`, even
returning the same thing and accepting the same options.

The pjax-specific keys listed in the `$(link).pjax()` section work here
as well.

This pjax call:

```js
$.pjax({
  url: '/authors',
  container: '#main'
})
```

Roughly translates into this ajax call:

```js
$.ajax({
  url: '/authors',
  dataType: 'html',
  beforeSend: function(xhr){
    xhr.setRequestHeader('X-PJAX', 'true')
  },
  success: function(data){
    $('#main').html(data)
    history.pushState(null, $(data).filter('title').text(), '/authors')
  })
})
```


## pjax on the server side

You'll want to give pjax requests a 'chrome-less' version of your page.
That is, the page without any layout.

As you can see in the "ajax call" example above, pjax sets a custom 'X-PJAX'
header to 'true' when it makes an ajax request to make detecting it easy.

In Rails, check for `request.headers['X-PJAX']`:

```ruby
def my_page
  if request.headers['X-PJAX']
    render :layout => false
  end
end
```

Or as a before filter in application controller:

```ruby
layout :set_layout

private
  def set_layout
    if request.headers['X-PJAX']
      false
    else
      "application"
    end
  end
```

Rails: <https://github.com/rails/pjax_rails>

Django: <https://github.com/jacobian/django-pjax>

Asp.Net MVC3: <http://biasecurities.com/blog/2011/using-pjax-with-asp-net-mvc3/>


## page titles

Your HTML should also include a `<title>` tag if you want page titles to work.

When using a page fragment, pjax will check the fragment DOM element
for a `title` or `data-title` attribute and use any value it finds.


## events

pjax will fire two events on the container you've asked it to load your
reponse body into:

* `pjax:start` - Fired when a pjax ajax request begins.
* `pjax:end`   - Fired when a pjax ajax request ends.

This allows you to, say, display a loading indicator upon pjaxing:

```js
$('a.pjax').pjax('#main')
$('#main')
  .on('pjax:start', function() { $('#loading').show() })
  .on('pjax:end',   function() { $('#loading').hide() })
```

Because these events bubble, you can also set them on the document:

```js
$('a.pjax').pjax()
$(document)
  .on('pjax:start', function() { $('#loading').show() })
  .on('pjax:end',   function() { $('#loading').hide() })
```

In addition, custom events are added to complement `$.ajax`'s
callbacks.

* `pjax:beforeSend` - Fired before the pjax request begins. Returning
                      false will abort the request.
* `pjax:complete`   - Fired after the pjax request finishes.
* `pjax:success`    - Fired after the pjax request succeeds.
* `pjax:error`      - Fired after the pjax request fails. Returning
                      false will prevent the the fallback redirect.
* `pjax:timeout`    - Fired if after timeout is reached. Returning
                      false will disable the fallback and will wait
                      indefinitely until the response returns.

**CAUTION** Callback handlers passed to `$.pjax` **cannot** be persisted
across full page reloads. Its recommended you use custom events instead.

## browser support

pjax only works with browsers that support the history.pushState API.

For a table of supported browsers see: <http://caniuse.com/#search=pushstate>

To check if pjax is supported, use the `$.support.pjax` boolean.

When pjax is not supported, `$('a').pjax()` calls will do nothing (aka links
work normally) and `$.pjax({url:url})` calls will redirect to the given URL.


## install it

```
$ cd path/to/js
$ wget https://raw.github.com/defunkt/jquery-pjax/master/jquery.pjax.js
```

Then, in your HTML:

```html
<script src="path/to/js/jquery.pjax.js"></script>
```

Replace `path/to/js` with the path to your JavaScript directory,
e.g. `public/javascripts`.


## minimize it

```
curl \
  -d output_info=compiled_code \
  -d compilation_level=SIMPLE_OPTIMIZATIONS \
  -d code_url=https://github.com/defunkt/jquery-pjax/raw/master/jquery.pjax.js \
  http://closure-compiler.appspot.com/compile
```