ContentIndex

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The ContentIndex interface of the Content Index API allows developers to register their offline enabled content with the browser.

Properties

There are no properties of this interface.

Methods

ContentIndex.add
Registers an item with the content index.
ContentIndex.delete
Unregisters an item from the currently indexed content.
ContentIndex.getAll
Returns a Promise that resolves with an iterable list of content index entries.

Examples

Feature Detection and Interface Access

Here we get a reference to the ServiceWorkerRegistration, then check for the index property, which gives us access to the content index interface.

// reference registration
const registration = await navigator.serviceWorker.ready;

// feature detection
if ('index' in registration) {

  // Content Index API functionality
  const contentIndex = registration.index;

}

Adding to the Content Index

Here we're declaring an item in the correct format and creating an asynchronous function which uses the add() method to register it with the content index.

// our content
const item = {
  id: 'post-1',
  url: '/posts/amet.html',
  title: 'Amet consectetur adipisicing',
  description: 'Repellat et quia iste possimus ducimus aliquid a aut eaque nostrum.',
  icons: [{
    src: '/media/dark.png',
    sizes: '128x128',
    type: 'image/png',
  }],
  category: 'article'
};

// our asynchronous function to add indexed content
async function registerContent(data) {
  const registration = await navigator.serviceWorker.ready;
  
  // feature detect Content Index
	if (!registration.index) {
		return;
	}

  // register content
  try {
		await registration.index.add(data);
  } catch (e) {
    console.log('Failed to register content: ', e.message);
  }
}

Retrieving Items Within The Current Index

The below example shows an asynchronous function that retrieves items within the content index and iterates over each entry, building a list for the interface.

async function createReadingList() {
  // access our service worker registration
  const registration = await navigator.serviceWorker.ready;

  // get our index entries
  const entries = await registration.index.getAll();

  // create a containing element
  const readingListElem = document.createElement('div');

  // test for entries
  if (!Array.length) {

    // if there are no entries, display a message
    const message = document.createElement('p');
    message.innerText = 'You currently have no articles saved for offline reading.'

    readingListElem.append(message);

  } else {

    // if entries are present, display in a list of links to the content
    const listElem = document.createElement('ul');

    for (const entry of entries) {
      const listItem = document.createElement('li');

      const anchorElem = document.createElement('a');
      anchorElem.innerText = entry.title;
      anchorElem.setAttribute('href', entry.url);

      listElem.append(listItem);

    }

    readingListElem.append(listElem);
  }

}

Unregistering Indexed Content

Below is an asynchronous function, that removes an item from the content index.

async function unregisterContent(article) {

  // reference registration
  const registration = await navigator.serviceWorker.ready;
  
  // feature detect Content Index
  if (!registration.index)
    return;

  // unregister content from index
  await registration.index.delete(article.id);
}

All the above methods are available within the scope of the service worker. They are accessible from the WorkerGlobalScope.self property:

// service worker script

self.registration.index.add(item);

self.registration.index.delete(item.id);

const contentIndexItems = self.registration.index.getAll();

Specifications

Specification Status Comment
Content Index API
The definition of 'ContentIndex' in that specification.
Editor's Draft Initial definition.

Browser compatibility

Update compatibility data on GitHub
DesktopMobile
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung Internet
ContentIndex
Experimental
Chrome No support NoEdge Full support 84Firefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android Full support 84Chrome Android Full support 84Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No
add
Experimental
Chrome No support NoEdge Full support 84Firefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android Full support 84Chrome Android Full support 84Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No
delete
Experimental
Chrome No support NoEdge Full support 84Firefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android Full support 84Chrome Android Full support 84Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No
getAll
Experimental
Chrome No support NoEdge Full support 84Firefox No support NoIE No support NoOpera No support NoSafari No support NoWebView Android Full support 84Chrome Android Full support 84Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support No

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.

See also: