Get PDFKit as base64 string - node.js

Question

I'm searching a way to get the base64 string representation of a PDFKit document. I cant' find the right way to do it...
Something like this would be extremely convenient.
var doc = new PDFDocument();
doc.addPage();
doc.outputBase64(function (err, pdfAsText) {
console.log('Base64 PDF representation', pdfAsText);
});
I already tried with blob-stream lib, but it doesn't work on a node server (It says that Blob doesn't exist).
Thanks for your help!

Answer 1

I was in a similar predicament, wanting to generate PDF on the fly without having temporary files lying around. My context is a NodeJS API layer (using Express) which is interacted with via a React frontend.
Ironically, a similar discussion for Meteor helped me get to where I needed. Based on that, my solution resembles:
const PDFDocument = require('pdfkit');
const { Base64Encode } = require('base64-stream');
// ...
var doc = new PDFDocument();
// write to PDF
var finalString = ''; // contains the base64 string
var stream = doc.pipe(new Base64Encode());
doc.end(); // will trigger the stream to end
stream.on('data', function(chunk) {
finalString += chunk;
});
stream.on('end', function() {
// the stream is at its end, so push the resulting base64 string to the response
res.json(finalString);
});

Answer 2

Synchronous option not (yet) present in the documentation
const doc = new PDFDocument();
doc.text("Sample text", 100, 100);
doc.end();
const data = doc.read();
console.log(data.toString("base64"));

Answer 3

I just made a module for this you could probably use. js-base64-file
const Base64File=require('js-base64-file');
const b64PDF=new Base64File;
const file='yourPDF.pdf';
const path=`${__dirname}/path/to/pdf/`;
const doc = new PDFDocument();
doc.addPage();
//save you PDF using the filename and path
//this will load and convert
const data=b64PDF.loadSync(path,file);
console.log('Base64 PDF representation', pdfAsText);
//you could also save a copy as base 64 if you wanted like so :
b64PDF.save(data,path,`copy-b64-${file}`);
It's a new module so my documentation isn't complete yet, but there is also an async method.
//this will load and convert if needed asynchriouniously
b64PDF.load(
path,
file,
function(err,base64){
if(err){
//handle error here
process.exit(1);
}
console.log('ASYNC: you could send this PDF via ws or http to the browser now\n');
//or as above save it here
b64PDF.save(base64,path,`copy-async-${file}`);
}
);
I suppose I could add in a convert from memory method too. If this doesn't suit your needs you could submit a request on the base64 file repo

Answer 4

Following Grant's answer, here is an alternative without using node response but a promise (to ease the call outside of a router):
const PDFDocument = require('pdfkit');
const {Base64Encode} = require('base64-stream');
const toBase64 = doc => {
return new Promise((resolve, reject) => {
try {
const stream = doc.pipe(new Base64Encode());
let base64Value = '';
stream.on('data', chunk => {
base64Value += chunk;
});
stream.on('end', () => {
resolve(base64Value);
});
} catch (e) {
reject(e);
}
});
};
The callee should use doc.end() before or after calling this async method.