How to use the docusign-esign.Document function in docusign-esign

try {
        var fs = require('fs');
        var path = require('path');
        // read file from a local directory
        fileBytes = fs.readFileSync(path.resolve(__dirname, SignTest1File));
      } catch (ex) {
        // TODO: handle error
        console.log('Exception: ' + ex);
      }

      // create an envelope that will store the document(s), field(s), and recipient(s)
      var envDef = new docusign.EnvelopeDefinition();
      envDef.setEmailSubject('Please sign this document sent from Node SDK)');

      // add a document to the envelope
      var doc = new docusign.Document();
      var base64Doc = Buffer.from(fileBytes).toString('base64');
      doc.setDocumentBase64(base64Doc);
      doc.setName('TestFile.pdf'); // can be different from actual file name
      doc.setDocumentId('1');

      var docs = [];
      docs.push(doc);
      envDef.setDocuments(docs);

      // add a recipient to sign the document, identified by name and email we used above
      var signer = new docusign.Signer();
      signer.setEmail(signerEmail);
      signer.setName(signerName);
      signer.setRecipientId('1');

      // Must set |clientUserId| for embedded recipients and provide the same value when requesting