How can I get a regular expression to match files ending in ".js" but not ".test.js"?

Question

I am using webpack which takes regular expressions to feed files into loaders. I want to exclude test files from build, and the test files end with .test.js. So, I am looking for a regular expression that would match index.js but not index.test.js.

I tried to use a negative lookback assertion with

/(?<!\.test)\.js$/

but it says that the expression is invalid.

SyntaxError: Invalid regular expression: /(?<!\.test)\.js$/: Invalid group

example files names:

index.js          // <-- should match
index.test.js     // <-- should not match
component.js      // <-- should match
component.test.js // <-- should not match

Narial

Not looked at webpack in a long time but I seem to remember that you can skip the regular expression and pass a function instead. Something like this in your case: function (path) { return path.endsWith('.js') && !path.endsWith('test.js')} I could be mixing this up with some other bundler though. – Germicide

Answer 1

var re=/^(?!.*test\.js).*\.js$/;
console.log(re.test("index.test.js"));
console.log(re.test("test.js"));
console.log(re.test("someother.js"));
console.log(re.test("testt.js"));

Canikin

Answer 2

There you go:

^(?!.*\.test\.js$).*\.js$

See it working on regex101.com.

---

As mentioned by others, the regex engine used by JavaScript does not support all features. For example, negative lookbehinds are not supported.

Grizel

My bad for disrupting your answer again, this is actually the best regex presented (ie the only one to have the end-of-line positional in the lookahead to not catch mid-string test.js ) – Dejected

Answer 3

Javascript doesn't support negative lookbehinds, but lookarounds:

^((?!\.test\.).)*\.js$

DEMO

Coverup

Answer 4

This may help:

^(?!.*\..*\.js$).*\.js$

Blasien

This does not address the question which is about excluding test files. – Coulter