PDFmake works on browser but IONIC no

Ionic Framework ionic-v3
1 
import pdfMake from "pdfmake/build/pdfmake";
import pdfFonts from "pdfmake/build/vfs_fonts";
pdfMake.vfs = pdfFonts.pdfMake.vfs;

public gerarPDF(){
        let texto = {
            content: 'PDF ORÇAMENTO 00001'
        }
        pdfMake.createPdf(texto).download();
}
2

Could you elaborate that error description a bit?
What does work where and where not?

3

This code works in the browser but does not work in the app (does not download the file)

4

i’m try it now:
message: ‘Property ‘writeFile’ does not exist on type ‘FileEntry | FileError’.
Property ‘writeFile’ does not exist on type ‘FileEntry’.’

public gerarPDF(){
        let cordova: any;
        let dd = null;
        dd = {content: ['AHH']};

         pdfMake.createPdf(dd).getBuffer((buffer) => {
         var utf8 = new Uint8Array(buffer); // Convert to UTF-8...
         let binaryArray = utf8.buffer; // Convert to Binary...

         let fileName = "file.pdf";
         let saveDir = cordova.file.externalApplicationStorageDirectory;

           File.createFile(saveDir, fileName, true).then((fileEntry) => {
             fileEntry.writeFile((fileWriter) => {
                 fileWriter.onwriteend = () => {
                 };
                 fileWriter.onerror = (e) => {
                     console.log('file writer - error event fired: ' + e.toString());
                 };
                 fileWriter.write(binaryArray);
             });
           });
         });
   }
5

What does that mean? ionic serve?

What does that mean?