How to convert files in Formidable Incomming form to base64

im building a next js project, basically it gets data from the client (form) and send it to the server through http request (axios) and then use xmlrpc to send it to odoo erp
the thing is that the form has files on it, what i want to do is send data and the files directly to odoo without storing them in my server, nota that odoo accepts only files with base64 encoding,
here is my frontend code

    const SubmitHandeler = (values) => {
        const formdata = new FormData();
        formdata.append('nom', values.nom);
        formdata.append('prenom', values.prenom);
        formdata.append('email', values.email);
        formdata.append('phone', values.phone);
        values.files.forEach((file) => {
            formdata.append(`file`, file);
        });
        setUploading(true);
        axios.post("/api/upload", formdata, {
            onUploadProgress: (progressEvent) => {
                const progressPercent = Math.round(
                    (progressEvent.loaded * 100) / progressEvent.total
                );
                setProgress(progressPercent);
            },
        }).then((result) => {
            setUploading(false);
            // router.push('/');
            console.log(result.data);
        }).catch((err) => {
            setUploading(false);
            console.log(err)
        });
    }

for my backend code, ive used formidable to parse the request, as u can see next, in the encoding option in the formidable.IncomingForm constructor, if i specify the format to base64, the resolved array of files will be empty (dont know why) but if i dont specify the encoding, the array of files got some actual files that i can store and i can work with them normally, but cant convert them into base64 although files in formidable (type : formidable.File) has a .toString() method but it doesnt let u specify the encoding (in fs for example we can do file.toString("base64") ), but in formidable we cant

export default async function handeler(req, res) {
    const form = new formidable.IncomingForm({ multiples: true, encoding: "base64" });

    const formData = new Promise((resolve, reject) => {
        form.parse(req, async (err, fields, files) => {
            if (err) {
                reject("error");
            }
            resolve({ fields, files });
        });
    });


    const { fields, files } = await formData;
    //SEND TO ODOO
    send_data_to_odoo(/*args*/)
    res.status(200).json({ msg: "done" })
}

• ive tried multer : dont suit me since multer stores files on the fs and i dont want that
• ive tried converting to base64 both in the frontend using js const base64String = Buffer.from(fileData).toString('base64'); but that didnt work
• ive tried to use file.toString() hoping odoo accepts it but no

You can use btoa to convert to the base64 format a string, and atob to decode a string from the base64 format.

In your next.js app (the frontend part), it looks like you aren't encoding the file to the base64 format, so you don't need to use encoding: "base64" on your api endpoint. Thus you should encode it on the backend.

export default async function handeler(req, res) {

    // you don't need to convert the files
    const form = new formidable.IncomingForm({ multiples: true });

    const formData = new Promise((resolve, reject) => {
        form.parse(req, async (err, fields, files) => {
            if (err) {
                reject("error");
            }
            resolve({ fields, files });
        });
    });


    const { fields, files } = await formData;

    // you convert each file to base64 format
    for (const file in files) {
      files[file] = btoa(files[file]);
    }

    //SEND TO ODOO
    send_data_to_odoo(/*args*/)
    res.status(200).json({ msg: "done" })
}

You can also verify that the file is not already encoded in base64 format with

let isBase64 = false;
try {
  // if you can convert the file from the base64 format, then the file is already encoded
  atob(files[file]);
  isBase64 = true;
} catch (err) {
  console.log('Already base64 format');
}

You can read the file and then use the Buffer toString() method passing "base64" as param.

Try this:

const formData = new Promise((resolve, reject) => {
  form.parse(req, async (err, fields, files) => {
    if (err) {
      reject("error");
    }

    Object.values(files).forEach((file) => {
      const buffer = fs.readFileSync(file.filepath);
      const base64 = buffer.toString("base64");
      console.log("File base64", base64.slice(0, 10));
    });
    
  });
});