node.js - Send binary pdf file with express -

im using html-pdf package node , need send file response. actual code on pdf.create function

pdf.create(html, options).tostream((err, stream) => {   if(err) throw err;   stream.pipe(fs.createwritestream(__dirname + '/gen.pdf'));     var file = fs.createreadstream(__dirname + '/gen.pdf');   //file.pipe(res);    res.setheader('content-type', 'application/pdf');   res.setheader('content-disposition', 'attachment; filename="gen.pdf"');   res.sendfile(__dirname+'/gen.pdf'); }); 

why not stream directly response? example:

pdf.create(html, options).tostream((err, stream) => {   if (err) throw err;   res.setheader('content-type', 'application/pdf');   res.setheader('content-disposition', 'attachment; filename="gen.pdf"');   stream.pipe(res); });