<script language="javascript" src="cadesplugin_api.js"></script>
<script>
    async function enc() {
        var oFile = document.getElementById("uploadFile").files[0];
        var selectedCert = await cadesplugin.CreateObjectAsync("CAdESCOM.Certificate");
        var dataCert = await fetch("m.cer");
        await selectedCert.Import(await dataCert.text());

        var reader = new FileReader();

        reader.onload = async function (ev) {
            console.log(ev);
            var header = ";base64,";
            var sFileData = reader.result;
            var sBase64Data = sFileData.substr(sFileData.indexOf(header) + header.length);
            var oEnvelop = await cadesplugin.CreateObjectAsync("CAdESCOM.CPEnvelopedData");
            await oEnvelop.propset_ContentEncoding(cadesplugin.CADESCOM_BASE64_TO_BINARY);
            await oEnvelop.propset_Content(sBase64Data);
            await (await oEnvelop.Recipients).Add(selectedCert);
            var data = await oEnvelop.Encrypt();
            var a = document.createElement("a");
            document.body.appendChild(a);
            let blob = new Blob([data], {
                type: "octet/stream",
            });

            let url = window.URL.createObjectURL(blob);
            a.href = url;
            a.download = oFile.name + ".p7e";
            a.click();
            window.URL.revokeObjectURL(url);
            document.body.removeChild(a);
        };
        reader.readAsDataURL(oFile);
    }

</script>
<input type="file" id="uploadFile" />
<button type="button" onclick="enc();">enc</button>