1.1.0 • Public • Published


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A tiny, ResizeObserver-based solution for building components responsive to their container size, rather than the viewport. The idea is to overcome the limitations of viewport-based media queries, and it's known as Container Queries.

Here is how it can be done, using this addon (controversial example):

    width-between-100-300=(hash width-gte=100 width-lte=300)
    bigSquare=(hash width-gt=500 height-gt=500 aspectRatio=1)
  as |RO|
  <p class='matchers {{if RO.is.bigSquare 'matchers--square'}}'>
    {{if RO.is.width-between-100-300 'Width is between 100px-300px'}}

  {{#if RO.is.bigSquare}}
    <p>Big square</p>

  {{#if (gt RO.width 300)}}
    <p>Width is greater than 300px</p>

  <p>Width: {{RO.width}}</p>
  <p>Height: {{RO.height}}</p>
  <p>Aspect Ratio: {{RO.aspectRatio}}</p>

This addon focuses on simplicity. It only includes a single component and won't do any attributes binding for you. Instead, it provides element's dimensions and easy to use size-matchers.


  • a single component and nothing more
  • only provides data (no attributes or class binding)
  • supports no-wrapper mode - use your element directly
  • easy to use size-matchers
  • works with FastBoot/SSR


ember install ember-resize-observer-component

If you need a ResizeObserver polyfill (caniuse.com):

ember install ember-resize-observer-polyfill


Matcher query syntax

Matchers allow you to map size-related conditions, such as width > 100, to properties on the object you get from <ResizeObserver /> (e.g. RO.is.large). And whenever the element's size changes, the relevant properties will update.

In the example below, large is a matcher name, and (hash width-gte=1200) represents a condition query.

<ResizeObserver @matchers={{hash large=(hash width-gte=1200)}} as |RO|>
  {{if RO.is.large "I'm large!"}}

Available operators: eq, gt, gte, lt, lte (they are similar to ember-truth-helpers)

Available conditions: width, height, aspectRatio.

Note: The addon protects you from mistyping by validating all your matchers and telling you exactly what was wrong with a particular matcher.

Query JavaScript
(hash width=10) width === 10
(hash width-gt=10) width > 10
(hash width-gte=10) width >= 10
(hash width-lt=10) width < 10
(hash width-lte=10) width <= 10

Examples with multiple values:

Query JavaScript
(hash width=10 height-lt=20) width === 10 && height < 20
(hash width-gt=10 aspectRatio=1) width > 10 && aspectRatio === 1

In no-wrapper mode, the component won't provide a wrapper element, so you will need to attach onResize handler to a target element yourself:

<ResizeObserver @noWrapper={{true}} as |RO|>
  <div {{on-resize RO.onResize}}>

You can set initial demensions that will be used if the component can't get element's size, e.g. in FastBoot environment:

  @matchers={{hash large=(hash width-gte=1200) square=(hash aspectRatio=1)}}
  as |RO|
  {{if RO.is.large 'Large'}}
  {{if RO.is.square 'Square'}}


For more info, please read the tests. The documentation will be improved soon.

Related addons

Alternative solutions worth checking out


See the Contributing guide for details.


  • Ember.js v3.20 or above
  • Ember CLI v3.20 or above
  • Node.js v12 or above


This project is licensed under the MIT License.



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