Description
Packagist is the main Composer repository. It aggregates public PHP packages installable with Composer:
https://getcomposer.org/
https://packagist.org/
It makes it easier to install and to keep up to date. If a developer is picking a library (vs another), package management is a criteria. More inclusions in apps means the library is used more, and can lead to more contributions (bug reports of course, but also hopefully patches and new features)
I know plotly.js is not in PHP, but it's common to have packages that have JavaScript but no PHP. This represents millions of downloads. Some notable ones:
https://packagist.org/packages/twbs/bootstrap
https://packagist.org/packages/components/jquery
https://packagist.org/packages/components/jqueryui
https://packagist.org/packages/blueimp/jquery-file-upload
https://packagist.org/packages/ckeditor/ckeditor
https://packagist.org/packages/mbostock/d3
https://packagist.org/packages/tinymce/tinymce
https://packagist.org/packages/moment/moment
Tiki gets dozens of them:
http://sourceforge.net/p/tikiwiki/code/HEAD/tree/trunk/composer.json
Thanks!