# Can Ember render only changes for block elements/helpers?

**URL:** <https://discuss.emberjs.com/t/can-ember-render-only-changes-for-block-elements-helpers/7627>\
**Category:** Uncategorized\
**Created:** [March 26, 2015, 11:52am UTC](https://discuss.emberjs.com/t/can-ember-render-only-changes-for-block-elements-helpers/7627 "2015-03-26T11:52:11Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![dmagunov](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dmagunov](https://discuss.emberjs.com/u/dmagunov)\
**Post date:** [March 26, 2015, 11:52am UTC](https://discuss.emberjs.com/t/can-ember-render-only-changes-for-block-elements-helpers/7627/1 "2015-03-26T11:52:11Z")

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Question to Ember gurus.

For example I have editable list of the items which generated via {{each}} helper, based on model collection. If I start to edit any item in the list and at the same time from the websocket connection it receives new item, then whole list rerendered and I lose my focus, data, and so on.

Is there a way in Ember to reconcile changes and update only what has actually changed, and not completely re-render everything.

Example:

> **[JS Bin](http://emberjs.jsbin.com/nanugu/1/edit?html,js,output)**
>
> A live pastebin for HTML, CSS & JavaScript and a range of processors, including SCSS, CoffeeScript, Jade and more...

Thanks.

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**Author:** ![Snake](https://avatars.discourse-cdn.com/v4/letter/s/50afbb/32.png) [@Snake](https://discuss.emberjs.com/u/Snake)\
**Post date:** [March 26, 2015, 2:30pm UTC](https://discuss.emberjs.com/t/can-ember-render-only-changes-for-block-elements-helpers/7627/2 "2015-03-26T14:30:23Z")

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This might help [http://dev.billysbilling.com/blog/How-to-optimize-inefficient-computed-properties-in-Ember-js](http://dev.billysbilling.com/blog/How-to-optimize-inefficient-computed-properties-in-Ember-js)

or wait until ember 2.0 then it will only re-render changed parts of the DOM.

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<div class="post-metadata">

**Author:** ![dmagunov](https://avatars.discourse-cdn.com/v4/letter/d/dfb087/32.png) [@dmagunov](https://discuss.emberjs.com/u/dmagunov)\
**Post date:** [March 26, 2015, 3:56pm UTC](https://discuss.emberjs.com/t/can-ember-render-only-changes-for-block-elements-helpers/7627/3 "2015-03-26T15:56:56Z")

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Thanks for the help, but I get following deprecation with this approach:

> DEPRECATION: Before observers are deprecated and will be removed in a future release. If you want to keep track of previous values you have to implement it yourself. See [http://emberjs.com/guides/deprecations/#toc\_deprecate-beforeobservers](http://emberjs.com/guides/deprecations/#toc_deprecate-beforeobservers) for more details.