Does ES6 import/export need ".js" extension?

The extension is part of the filename. You have to put it in.

As a proof try this:

• rename file to drawImage.test
• edit index.js to contain './drawImage.test'

Reload and you'll see the extendion js or test is completely arbirary, as long as you specify it in the export.

Obviously, after the test revert to the correct/better js extension.

No, modules don't care about extensions. It just needs to be a name that resolves to a source file.

In your case, http://localhost/bla/src/drawImage is not a file while http://localhost/bla/src/drawImage.js is, so that's where there error comes from. You can either add the .js in all your import statements, or configure your server to ignore the extension, for example. Webpack does the same. A browser doesn't, because it's not allowed to rewrite urls arbitrarily.

ES6 import/export need “.js” extension. There are clear instructions in node document:

1. Relative specifiers like './startup.js' or '../config.mjs'. They refer to a path relative to the location of the importing file. The file extension is always necessary for these.
2. This behavior matches how import behaves in browser environments, assuming a typically configured server.

https://nodejs.org/api/esm.html#esm_import_expressions