Change record status: 
Project: 
Introduced in branch: 
8.x
Description: 

For more detailed and up to date information and examples, please see https://www.drupal.org/node/2379475.

Now that scripts need to declare their dependencies in a library. The usual way of adding scripts to a theme does not work anymore. Themes must declare their scripts in a library and add them from the info file with the libraries key if they are required on all pages.

Drupal 8

mytheme.libraries.yml

scripts:
  version: VERSION
  js:
    js/base.js

mytheme.info.yml

…
core: 8.x
libraries:
  - mytheme/scripts
ckeditor_stylesheets:
  - css/ckeditor-iframe.css
…
Impacts: 
Module developers
Themers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done