Convert Blob data to Raw buffer in javascript or node

Question

I am using a plugin jsPDF which generates PDF and saves it to local file system. Now in jsPDF.js, there is some piece of code which generates pdf data in blob format as:-

var blob = new Blob([array], {type: "application/pdf"});

and further saves the blob data to local file system. Now instead of saving I need to print the PDF using plugin node-printer .

Here is some sample code to do so

var fs = require('fs'),
var dataToPrinter;

fs.readFile('/home/ubuntu/test.pdf', function(err, data){
    dataToPrinter = data;
}

var printer = require("../lib");
printer.printDirect({
    data: dataToPrinter,
    printer:'Deskjet_3540',
    type: 'PDF',
    success: function(id) {
        console.log('printed with id ' + id);
    },
    error: function(err) {
        console.error('error on printing: ' + err);
    }
})

The fs.readFile() reads the PDF file and generates data in raw buffer format.

Now what I want is to convert the 'Blob' data into 'raw buffer' so that I can print the PDF.

Answer 1

           var blob = new Blob([array], {type: "application/pdf"});

            var arrayBuffer, uint8Array;
            var fileReader = new FileReader();
            fileReader.onload = function() {
                arrayBuffer = this.result;
                uint8Array  = new Uint8Array(arrayBuffer);

                var printer = require("./js/controller/lib");
                printer.printDirect({
                    data: uint8Array,
                    printer:'Deskjet_3540',
                    type: 'PDF',
                    success: function(id) {
                        console.log('printed with id ' + id);
                    },
                    error: function(err) {
                        console.error('error on printing: ' + err);
                    }
                })
            };
            fileReader.readAsArrayBuffer(blob);

This is the final code which worked for me. The printer accepts uint8Array encoding format.

Answer 2

For me, it worked with the following:

const buffer=Buffer.from(blob,'binary');

So, this buffer can be stored in Google Cloud Storage and local disk with fs node package.

I used blob file, to send data from client to server through ddp protocol (Meteor), so, when this file arrives to server I convert it to buffer in order to store it.

Answer 3

If you are not using NodeJS then you should know that the browser does not have a Buffer class implementation and you are probably compiling your code to browser-specific environment on something like browserify. In that case you need this library that converts your blob into a Buffer class that is supposed to be as perfectly equal to a NodeJS Buffer object as possible (the implementation is at feross/buffer ).

If you are using node-fetch (not OP's case) then you probably got a blob from a response object:

const fetch = require("node-fetch");
const response = await fetch("http://www.stackoverflow.com/");
const blob = await response.blob();

This blob is an internal implementation and exists only inside node-fetch or fetch-blob libraries, to convert it to a native NodeJS Buffer object you need to transform it to an arrayBuffer first:

const arrayBuffer = await blob.arrayBuffer();
const buffer = Buffer.from(arrayBuffer);

This buffer object can then be used on things such as file writes and server responses.

Answer 4

Try:

var blob = new Blob([array], {type: "application/pdf"});
var buffer = new Buffer(blob, "binary");