pjax = pushState + ajax, Yii 2.0 fork with enhancements

pjax is a jQuery plugin that uses ajax and pushState to deliver a fast browsing experience with real permalinks, page titles, and a working back button.

pjax works by fetching HTML from your server via ajax and replacing the content
of a container element on your page with the loaded HTML. It then updates the
current URL in the browser using pushState. This results in faster page
navigation for two reasons:

* No page resources (JS, CSS) get re-executed or re-applied;
* If the server is configured for pjax, it can render only partial page
contents and thus avoid the potentially costly full layout render.

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jquery-pjax is largely unmaintained at this point. It might continue to
receive important bug fixes, but _its feature set is frozen_ and it's unlikely
that it will get new features or enhancements.

Installation

pjax depends on jQuery 1.8 or higher.

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There's no need to install library manually since it comes pre-installed with Yii 2.0.

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``
$ bower install yii2-pjax
`

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Or, add yii2-pjax to your app's bower.json.

` json
"dependencies": {
"yii2-pjax": "latest"
}
`

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pjax can be downloaded directly into your app's public directory - just be sure you've loaded jQuery first.
Download and include jquery.pjax.js in your web page:

`
curl -LO https://raw.github.com/yiisoft/jquery-pjax/master/jquery.pjax.js
`

Usage

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The simplest and most common use of pjax looks like this:

` javascript
$(document).pjax('a', '#pjax-container')
`

This will enable pjax on all links on the page and designate the container as #pjax-container.

If you are migrating an existing site, you probably don't want to enable pjax
everywhere just yet. Instead of using a global selector like a, try annotating
pjaxable links with data-pjax, then use 'a[data-pjax]' as your selector. Or,
try this selector that matches any links inside a data-pjax> container:

` javascript
$(document).pjax('[data-pjax] a, a[data-pjax]', '#pjax-container')
`

#### Server-side configuration

Ideally, your server should detect pjax requests by looking at the special
X-PJAX HTTP header, and render only the HTML meant to replace the contents of
the container element (#pjax-container in our example) without the rest of
the page layout. Here is an example of how this might be done in Ruby on Rails:

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

If you'd like a more automatic solution than pjax for Rails check out [Turbolinks][].

[Check if there is a pjax plugin][plugins] for your favorite server framework.

Also check out [RailsCasts #294: Playing with PJAX][railscasts].

#### Arguments

The synopsis for the $.fn.pjax function is:

` javascript
$(document).pjax(selector, [container], options)
`

1. selector is a string to be used for click [event delegation][$.fn.on].
2. container is a string selector that uniquely identifies the pjax container.
3. options is an object with keys described below.

##### pjax options

key | default | description
----|---------|------------
timeout | 650 | ajax timeout in milliseconds after which a full refresh is forced
push | true | use [pushState][] to add a browser history entry upon navigation
replace | false | replace URL without adding browser history entry
maxCacheLength | 20 | maximum cache size for previous container contents
version | | a string or function returning the current pjax version
scrollTo | 0 | vertical position to scroll to after navigation. To avoid changing scroll position, pass false. If set to true page will scroll to the pjax container. Can also be be a callback function with context and current hash passed in as parameters. E.g. function (context, hash) { if (!hash) return $(context).offset().top; }
scrollOffset | 0 | vertical offset that gets added to scrollTo. Can be a callback function with the current scrollTo value passed as a parameter.
type | "GET" | see [$.ajax][]
dataType | "html" | see [$.ajax][]
container | | CSS selector for the element where content should be replaced
url | link.href | a string or function that returns the URL for the ajax request
target | link | eventually the relatedTarget value for pjax events
fragment | | CSS selector for the fragment to extract from ajax response
pushRedirect | false | whether to add a browser history entry upon redirect
replaceRedirect | true | whether to replace URL without adding a browser history entry upon redirect
skipOuterContainers | false | When pjax containers are nested and this option is true, the closest pjax block will handle the event. Otherwise, the top container will handle the event
ieRedirectCompatibility | true | Whether to add X-Ie-Redirect-Compatibility header for the request on IE. Fixes IE error on 302 redirect without Location header

You can change the defaults globally by writing to the $.pjax.defaults object:

` javascript
$.pjax.defaults.timeout = 1200
`

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This is a lower level function used by $.fn.pjax itself. It allows you to get a little more control over the pjax event handling.

This example uses the current click context to set an ancestor element as the container:

` javascript
if ($.support.pjax) {
$(document).on('click', 'a[data-pjax]', function(event) {
var container = $(this).closest('[data-pjax-container]')
var containerSelector = '#' + container.id
$.pjax.click(event, {container: containerSelector})
})
}
`

NOTE Use the explicit $.support.pjax guard. We aren't using $.fn.pjax so we should avoid binding this event handler unless the browser is actually going to use pjax.

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Submits a form via pjax.

` javascript
$(document).on('submit', 'form[data-pjax]', function(event) {
$.pjax.submit(event, '#pjax-container')
})
`

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Initiates a request for the current URL to the server using pjax mechanism and replaces the container with the response. Does not add a browser history entry.

` javascript
$.pjax.reload('#pjax-container', options)
`

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Manual pjax invocation. Used mainly when you want to start a pjax request in a handler that didn't originate from a click. If you can get access to a click event, consider $.pjax.click(event) instead.

` javascript
function applyFilters() {
var url = urlForFilters()
$.pjax({url: url, container: '#pjax-container'})
}
`

Events

All pjax events except pjax:click & pjax:clicked are fired from the pjax
container element.

pjax:send & pjax:complete are a good pair of events to use if you are implementing a
loading indicator. They'll only be triggered if an actual XHR request is made,
not if the content is loaded from cache:

` javascript
$(document).on('pjax:send', function() {
$('#loading').show()
})
$(document).on('pjax:complete', function() {
$('#loading').hide()
})
`

An example of canceling a pjax:timeout event would be to disable the fallback
timeout behavior if a spinner is being shown:

` javascript
$(document).on('pjax:timeout', function(event) {
// Prevent default timeout redirection behavior
event.preventDefault()
})
`

Advanced configuration

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The whole point of pjax is that it fetches and inserts new content _without_
refreshing the page. However, other jQuery plugins or libraries that are set to
react on page loaded event (such as DOMContentLoaded) will not pick up on
these changes. Therefore, it's usually a good idea to configure these plugins to
reinitialize in the scope of the updated page content. This can be done like so:

` js
$(document).on('ready pjax:end', function(event) {
$(event.target).initializeMyPlugin()
})
`

This will make $.fn.initializeMyPlugin() be called at the document level on
normal page load, and on the container level after any pjax navigation (either
after clicking on a link or going Back in the browser).

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By default, pjax will force a full reload of the page if it receives one of the
following responses from the server:

* Page content that includes when fragment selector wasn't explicitly
configured. Pjax presumes that the server's response hasn't been properly
configured for pjax. If fragment pjax option is given, pjax will extract the
content based on that selector.

* Page content that is blank. Pjax assumes that the server is unable to deliver
proper pjax contents.

* HTTP response code that is 4xx or 5xx, indicating some server error.

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If the server needs to affect the URL which will appear in the browser URL after
pjax navigation (like HTTP redirects work for normal requests), it can set the
X-PJAX-URL header:

` ruby
def index
request.headers['X-PJAX-URL'] = "http://example.com/hello"
end
`

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Layouts can be forced to do a hard reload when assets or html changes.

First set the initial layout version in your header with a custom meta tag.

` html

`

Then from the server side, set the X-PJAX-Version header to the same.

` ruby
if request.headers['X-PJAX']
response.headers['X-PJAX-Version'] = "v123"
end
``

Deploying a deploy, bumping the version constant to force clients to do a full reload the next request getting the new layout and assets.

[$.fn.on]: http://api.jquery.com/on/
[$.ajax]: http://api.jquery.com/jQuery.ajax/
[pushState]: https://developer.mozilla.org/en-US/docs/Web/Guide/API/DOM/Manipulating_the_browser_history#Adding_and_modifying_history_entries
[plugins]: https://gist.github.com/4283721
[turbolinks]: https://github.com/rails/turbolinks
[railscasts]: http://railscasts.com/episodes/294-playing-with-pjax