Webstorm not recognising JavaScript file

So I see three possible reasons for the problem:

1. The file was marked as 'Plain text'

2. There is a pattern for 'Text files' file type that matches this file (or back: file type 'JavaScript' exclude this file name). See image below

3. There is a custom plugin that overrides default behavior for files with this name (unlikely)

Updated: after several years I've found one more reason for the behavior and most likely it the main source of the issues. When you create a file without any extensions the "Register New File Type Association" is appeared. And you can accidentally specify a new file type, for some file name. It is can be fixed with (2) but it is the reason why the pattern was added there.

Note: the solution works for all IDEA-based IDEs: IntelliJ IDEA, WebStorm, RubyMine, PyCharm, PhpStorm.

My problem was with Auto-detect file type by context

If the file was marked as "Plain Text", then this can be fixed as follows:

1. Right click on the file.

2. One of the menu options is "Mark as Javascript" . Just below "Delete".

3. Click that. Your file is now recognized as javascript by WebStorm.

Since WebStorm was not allowing screenshots after right click so couldn't add it here.

File -> Settings -> Editor -> FileTypes -> Text files -> check for "ContentRepository.js" pattern there and remove it.