at-most-one

```html <at-most-one attribute=data-selected> <iframe name=view1 data-selected></iframe> <iframe name=view2></iframe> <iframe name=view2></iframe> </at-most-one> <script> document.querySelector('[view2]').setAttribute('data-selected', ''); </script> ```

Usage no npm install needed!

<script type="module">
  import atMostOne from 'https://cdn.skypack.dev/at-most-one';
</script>

README

at-most-one

<at-most-one attribute=data-selected>
    <iframe name=view1 data-selected></iframe>
    <iframe name=view2></iframe>
    <iframe name=view2></iframe>
</at-most-one>
<script>
document.querySelector('[view2]').setAttribute('data-selected', '');
</script>

This will cause data-selected attribute on view1 to go away.