A Client Side Includes tag.
$ npm install --save @github/include-fragment-element
include-fragment elements must have a
src attribute from which to retrieve an HTML element fragment.
The initial page load should include fallback content to be displayed if the resource could not be fetched immediately.
<div class="tip"> <include-fragment src="/tips"> <p>Loading tip…</p> </include-fragment> </div>
On page load, the
include-fragment element fetches the URL, the response is parsed into an HTML element, which replaces the
include-fragment element entirely.
<div class="tip"> <p>You look nice today</p> </div>
The server must respond with an HTML fragment to replace the
include-fragment element. It should not contain another
include-fragment element or the server will be polled in an infinite loop.
This attribute tells
<include-fragment/> what to send as the
Accept header, as part of the fetch request. If omitted, or if set to an empty value, the default behaviour will be
text/html. It is important that the server responds with HTML, but you may wish to change the accept header to help negotiate the right content with the server.
This indicates when the contents should be fetched:
eager: Fetches and load the content immediately, regardless of whether or not the
<include-fragment/>is currently within the visible viewport (this is the default value).
lazy: Defers fetching and loading the content until the
<include-fragment/>tag reaches a calculated distance from the viewport. The intent is to avoid the network and storage bandwidth needed to handle the content until it's reasonably certain that it will be needed.
If the URL fails to load, the
include-fragment element is left in the page and tagged with an
is-error CSS class that can be used for styling.
Request lifecycle events are dispatched on the
loadstart- The server fetch has started.
load- The request completed successfully.
error- The request failed.
loadend- The request has completed.
include-fragment-replace(cancelable) - The success response has been parsed. It comes with
event.detail.fragmentthat will replace the current element.
include-fragment-replaced- The element has been replaced by the fragment.
const loader = document.querySelector('include-fragment') const container = loader.parentElement loader.addEventListener('loadstart', () => container.classList.add('is-loading')) loader.addEventListener('loadend', () => container.classList.remove('is-loading')) loader.addEventListener('load', () => container.classList.add('is-success')) loader.addEventListener('error', () => container.classList.add('is-error'))
||URL string||Required URL from which to load the replacement HTML element fragment.|
The request for replacement markup from the server starts when the
src attribute becomes available on the
<include-fragment> element. Most often this will happen at page load when the element is rendered. However, if we omit the
src attribute until some later time, we can defer loading the content at all.
<details-menu> element uses this technique to defer loading menu content until the menu is first opened.
Deferring the display of markup is typically done in the following usage patterns.
A user action begins a slow running background job on the server, like backing up files stored on the server. While the backup job is running, a progress bar is shown to the user. When it's complete, the include-fragment element is replaced with a link to the backup files.
The first time a user visits a page that contains a time-consuming piece of markup to generate, a loading indicator is displayed. When the markup is finished building on the server, it's stored in memcache and sent to the browser to replace the include-fragment loader. Subsequent visits to the page render the cached markup directly, without going through a include-fragment element.
Relation to Server Side Includes
<include-fragment src="/github/include-fragment/commit-count" timeout="100"> <p>Counting commits…</p> </include-fragment>
A proxy may attempt to fetch and replace the fragment if the request finishes before the timeout. Otherwise the tag is delivered to the client. This library only implements the client side aspect.
- Microsoft Edge
npm install npm test
Distributed under the MIT license. See LICENSE for details.