[Pkg-javascript-devel] Questions about using ES modules in CJS.

[Pirate Praveen]

On ചൊ, മേയ് 3 2022 at 06:41:01 വൈകു +0800 +0800, 
Ying-Chun Liu (PaulLiu) <paulliu at debian.org> wrote:
> Hi Praveen,
> 
>  Sorry for bothering but I just got lots of questions about using ES 
> modules and I'm not sure who to ask. I tried to read the history of 
> Debian wiki pages about ES modules and found you.
> 
> 
> Recently I've updated node-leven package to the latest upstream 
> version and it becomes an ES module now.
>  To use ES modules, I wrote a simple "mjs" script file:
> 
> import leven from '/usr/share/nodejs/leven/index.js';
>  console.log(leven('test', 'test2')); // output: 1
> 
> 
> The first question is why I cannot use "import leven from 'leven';"?
> 
I think that is how ES module standard is supposed to work. You can add 
a symlink to node_modules

mkdir -p node_modules
ln -s /usr/share/nodejs/leven node_modules

There is debian/nodejs/extlinks in pkg-js-tools to help with this 
symlink creation.

I think Jeremy Lal mentioned in the past that global path for ES 
modules will not be supported.
> I got ERR_MODULE_NOT_FOUND if I don't use the full path.
> 
> But packages like assert works without full path.
>  Not sure if I got things wrong.
> 
> 
> The second question is more complicated.
>  I tried to use leven from a CJS module.
>  It works if I use dynamic import with full path:
> 
> var leven;
>  async function test() {
>     leven = await import ('/usr/share/nodejs/leven/index.js');
>     leven = leven.default;
>     console.log(leven('test', 'test1')); // output 1
>  }
>  test();
> 
>  However, it seems to me that with CJS, there's no top-level await.
>  So I can only wrapping things in an async function.
> 
>  But this is a bit trouble. How can I simply convert require('leven') 
> used in node-commist if there's no top-level await?
>  I cannot wrap whole node-commist inside an async function because it 
> should work like a library.
> 
>  Yours,
>  Paul
>