In my api
router, there is a function called generatePDF
which aims to use PDFKit module to generate a PDF file in memory and send to client for download instead of displaying only.
In api.js
:
var express = require('express');
var router = express.Router();
const PDFDocument = require('pdfkit');
router.get('/generatePDF', async function(req, res, next) {
var myDoc = new PDFDocument({bufferPages: true});
myDoc.pipe(res);
myDoc.font('Times-Roman')
.fontSize(12)
.text(`this is a test text`);
myDoc.end();
res.writeHead(200, {
'Content-Type': 'application/pdf',
'Content-disposition': 'attachment;filename=test.pdf',
'Content-Length': 1111
});
res.send( myDoc.toString('base64'));
});
module.exports = router;
This does not work. The error message is (node:11444) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
.
How can I go about fixing the issue and getting it work?
Also, a relevant question would be how I can separate the business logic of PDF generation from the router and chain them up?
Complete solution.
var express = require('express');
var router = express.Router();
const PDFDocument = require('pdfkit');
router.get('/generatePDF', async function(req, res, next) {
var myDoc = new PDFDocument({bufferPages: true});
let buffers = [];
myDoc.on('data', buffers.push.bind(buffers));
myDoc.on('end', () => {
let pdfData = Buffer.concat(buffers);
res.writeHead(200, {
'Content-Length': Buffer.byteLength(pdfData),
'Content-Type': 'application/pdf',
'Content-disposition': 'attachment;filename=test.pdf',})
.end(pdfData);
});
myDoc.font('Times-Roman')
.fontSize(12)
.text(`this is a test text`);
myDoc.end();
});
module.exports = router;