Fixed #22463 -- Added code style guide and JavaScript linting (EditorConfig and ESLint)

docs/internals/contributing/writing-code/javascript.txt

@@ -0,0 +1,64 @@
+==========
+JavaScript
+==========
+
+While most of Django core is Python, the ``admin`` and ``gis`` contrib apps
+contain JavaScript code.
+
+Please follow these coding standards when writing JavaScript code for inclusion
+in Django.
+
+Code style
+----------
+
+* Please conform to the indentation style dictated in the ``.editorconfig``
+  file. We recommend using a text editor with `EditorConfig`_ support to avoid
+  indentation and whitespace issues. Most of the JavaScript files use 4 spaces
+  for indentation, but there are some exceptions.
+
+* When naming variables, use ``camelCase`` instead of ``underscore_case``.
+  Different JavaScript files sometimes use a different code style. Please try to
+  conform to the code style of each file.
+
+* Use the `JSHint`_ code linter to check your code for bugs and style errors.
+  JSHint will be run when you run the JavaScript tests. We also recommended
+  installing a JSHint plugin in your text editor.
+
+.. _javascript-patches:
+
+JavaScript patches
+------------------
+
+Django's admin system leverages the jQuery framework to increase the
+capabilities of the admin interface. In conjunction, there is an emphasis on
+admin JavaScript performance and minimizing overall admin media file size.
+Serving compressed or "minified" versions of JavaScript files is considered
+best practice in this regard.
+
+To that end, patches for JavaScript files should include both the original
+code for future development (e.g. ``foo.js``), and a compressed version for
+production use (e.g. ``foo.min.js``). Any links to the file in the codebase
+should point to the compressed version.
+
+Compressing JavaScript
+~~~~~~~~~~~~~~~~~~~~~~
+
+To simplify the process of providing optimized JavaScript code, Django
+includes a handy Python script which should be used to create a "minified"
+version. To run it::
+
+    python django/contrib/admin/bin/compress.py
+
+Behind the scenes, ``compress.py`` is a front-end for Google's
+`Closure Compiler`_ which is written in Java. However, the Closure Compiler
+library is not bundled with Django directly, so those wishing to contribute
+complete JavaScript patches will need to download and install the library
+independently. The Closure Compiler library requires `Java`_ 7 or higher.
+
+Please don't forget to run ``compress.py`` and include the ``diff`` of the
+minified scripts when submitting patches for Django's JavaScript.
+
+.. _Closure Compiler: https://developers.google.com/closure/compiler/
+.. _EditorConfig: http://editorconfig.org/
+.. _Java: https://www.java.com
+.. _jshint: http://jshint.com/