0.0.7 • Public • Published


Published on webcomponents.org

File size of all components combined

The ob-session package contains three references to make storing objects in SessionStorage easier and faster:

  1. A small "api" that enhances the sessionStorage.setItem, sessionStorage.getItem and sessionStorage.removeItem calls to support storing objects, not just strings, in a performant way. Objects are stored in a global cache for rapid retrieval, but a stringified version is stored in sessionStorage for when the page is refreshed. This is not done on low memory devices however. It is only done if the code can confirm that the device has > 1 Gig RAM.
  2. A non-visual web component, "ob-session-watch", that watches for sessionStorage changes, and fires an event when such a thing happens. It can watch for all changes, or to those with a specified key.
  3. A non-visual web component, "ob-session-update", that updates sessionStorage declaratively.

In good company

Websites that appear to store objects in session storage:

  1. Twitter.com
  2. Amazon.com
  3. Walmart.com
  4. CNN.com
  5. WashingtonPost.com
  6. TypescriptLang.org
  7. WSJ.com

Why focus on Session Storage?

Whereas one could argue that local storage is being eclipsed by helper libraries based on Indexed DB, session storage serves a particular niche -- In some lines of business, caching business data in the client, even after the browser window / tab closes, runs afoul of audits. history.state and sessionStorage don't appear to raise such concerns.


The api supports an init(win: Window) function, where you can pass in a window (say, from an iframe). init() is immediately called on the window that references the api.

Once init is called, just call setItem(key, stringOrJsonSerializableObject), getItem(key), removeItem(key) from the window object.

To listen for any updates to sessionStorage, use:

win.addEventListener('session-storage-item-set', e => {
    console.log(e.detail.oldValue, e.detail.newValue, e.detail.key);
win.addEventListener('session-storage-item-removed', e => {
    console.log(e.detail.oldValue, e.detail.key);

where "win" is a local variable shortcut pointing to the (iframed) window object.


<ob-session-update key="myObj" val='{"greeting": "hello"}' is-json></ob-session-update>
<ob-session-watch key="myObj" id=myWatcher></ob-session-watch>

Api Reference

Viewing Your Element

$ npm install
$ npm run serve

Running Tests





Package Sidebar


npm i ob-session

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  • bahrus