How does this pattern work: 'test/e2e/**/*.spec.js'?

Question

I saw this pattern used in a configuration file for protractor.

specs: [
  'test/e2e/**/*.spec.js'
]

To mean it means "all files inside test/e2e". What kind of pattern is this? I think it's not regex because of those unescaped slashes. Especially, why is there ** in the middle, not just test/e2e/*.spec.js?

I tried using the search engine, but did not find anything useful probably because the asterisks don't work very well in search engines.

Answer 1

What kind of pattern is this?

It is called "glob". The module glob is a popular implementation for Node, and appears to be the one used by Protractor.

Especially, why is there "**" in the middle, not just "test/e2e/*.spec.js"?

** means it can match sub-directories. It's like a wildcard for sub-directories.

For example, test/e2e/*.spec.js would match test/e2e/example.spec.js, but not test/e2e/subdir/example.spec.js. However test/e2e/**/*.spec.js matches both.