What does ** mean in a path?
/path/to/file/**/*.js matches any number of directories between /path/to/file/ and /*.js. As opposed to /path/to/file/*/*.js, which matches a single directory between /path/to/file/ and /*.js.
this matchers called "glob pattern" they are widely used in shell script and in CLI tools like grunt or npm .they '**' means -- "Matches zero or more directories, but will never match the directories . and .. "you can read more in the docsglob pattern