Get composer to accept external Javascript libraries hosted on packagist

install.md

Composer (recommended) If you would like to install the select2 library with composer, you probably used the drupal composer template to set up your project. It's recommended to use asset-packagist to install JavaScript libraries. So you will need to add the following to your composer.json file into the repositories section:

    {
        "type": "composer",
        "url": "https://asset-packagist.org"
    }

It's also needed to extend the 'installer-path' section:

    "web/libraries/{$name}": [
        "type:drupal-library",
        "type:bower-asset",
        "type:npm-asset"
    ],

And add a new 'installer-types' section next to the 'installer-path' in the 'extra' section:

    "installer-types": [
      "bower-asset",
      "npm-asset"
    ],

Be mindful of comma's! After this you can install the library with composer require oomphinc/composer-installers-extender npm-asset/select2 and the library will be downloaded into the libraries folder.

Expanded example

   "installer-paths": {
      "web/core": [
        "type:drupal-core"
      ],
      "web/libraries/{$name}": [
        "type:drupal-library",
        "type:bower-asset",
        "type:npm-asset"
      ],
      "web/modules/contrib/{$name}": [
        "type:drupal-module"
      ],
      "web/profiles/contrib/{$name}": [
        "type:drupal-profile"
      ],
      "web/themes/contrib/{$name}": [
        "type:drupal-theme"
      ],
      "drush/Commands/contrib/{$name}": [
        "type:drupal-drush"
      ],
      "web/modules/custom/{$name}": [
        "type:drupal-custom-module"
      ],
      "web/profiles/custom/{$name}": [
        "type:drupal-custom-profile"
      ],
      "web/themes/custom/{$name}": [
        "type:drupal-custom-theme"
      ]
    },
    "installer-types": [
      "bower-asset",
      "npm-asset"
    ],

Repositories example

  "repositories": {
    "drupal": {
      "type": "composer",
      "url": "https://packages.drupal.org/8"
    },
    "javascript": {
      "type": "composer",
      "url": "https://asset-packagist.org"
    },
    "magnific-popup": {
      "type": "vcs",
      "url": "https://github.com/dimsemenov/magnific-popup"
    },
    "chosen": {
      "type": "vcs",
      "url": "https://github.com/harvesthq/chosen"
    },
    "spectrum": {
      "type": "vcs",
      "url": "[email protected]:df-a/spectrum.git"
    },
    "slick": {
      "type": "vcs",
      "url": "[email protected]:df-a/slick.git"
    },
    "jquery-easing": {
      "type": "vcs",
      "url": "[email protected]:df-a/jquery.easing.git"
    },
    "blazy": {
      "type": "vcs",
      "url": "[email protected]:df-a/blazy.git"
    },
    "novacancy": {
      "type": "vcs",
      "url": "[email protected]:df-a/novacancy.js.git"
    },
    "editormd": {
      "type": "vcs",
      "url": "[email protected]:unicorn-fail/editor.md.git"
    },
    "select2": {
      "type": "vcs",
      "url": "[email protected]:select2/select2.git"
    }
  },