Fs createWriteStream doesn't work with assets?

I’m not so expert with fs of node.js, but I tried to do a thing like this, following the example in this module : html-convert - npm to convert html to gif, in async function :

 var htmlConvert = require('html-convert');
 var fs = require('fs');

 var convert = htmlConvert({
    fetchTimeout: 10000,
    renderTimeout: 3000,
    format: 'gif',
    width: 607,
    height: 403,
    phantomFlags: ['--ignolsre-ssl-errors=true'],
    maxRenders: 1000,
 });

 await fs.createReadStream('public/profilogif.html')
   .pipe(convert())
   .pipe(fs.createWriteStream("assets/profilogif.gif"));

But it threw this error

And so I removed this part

    .pipe(fs.createWriteStream("assets/profilogif.gif"));

and the error was not thrown anymore.
So, I think that the problem is the assets folder. Any idea?

Do you are trying to create the file in the default assets folder? If so, this is impossible since assets is not really a folder, it just list all your project files which are in the Glitch CDN.

A file with that name already exists in the folder, but I don’t know if referencing to it with his name works(it’s name is “profilogif.gif”).

If you have an assets folder locally, then try a direct rather than relative reference to the directory e.g. __dirname + '/assets/profilogif.gif' If as NikoBotDev mentioned, you’re referring to ‘assets’ in the Glitch editor, then that’s a virtual folder so you’ll create the folder locally first.

So I should create a local folder, then?
Ok, I’ll try that! Thank you for your help.