css-observe

Fire a custom event whenever an element matching a specified selector is added to the (shadow dom) realm in which the instance is added. Optionally, clone a template inside.

API Reference

<script type="module" src="https://cdn.pika.dev/css-observe"></script>
<div>
    <script type="module" src="https://cdn.pika.dev/css-observe"></script>
    <css-observe observe selector="div[test]" clone>
        <template>Found it</template>
    </css-observe>
    <div test>
        I am here
    </div>
</div>

Another attribute / property, within-closest/withinClosest, restricts matches to those within the closest ancestry of the css-observe element matching the within-closest value.

css-observe will fire event: latest-match-changed, and the newly added element can be obtained from event.detail.value.

It will only observe the selector within the same Shadow DOM realm where the element is placed. If the element is placed outside any ShadowDOM, it will observe the selector only outside any ShadowDOM. How cool is that?

Implementation

Based off of an idea found here

Viewing Your Element

$ npm install
$ npm run serve

Running Tests

$ npm run test