You can decode the base64 image using following method .

EDITED

To strip off the header

let base64String = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgA'; // Not a real image
// Remove header
let base64Image = base64String.split(';base64,').pop();

To write to a file

import fs from 'fs';
fs.writeFile('image.png', base64Image, {encoding: 'base64'}, function(err) {
    console.log('File created');
});

Note :- Don’t forget the {encoding: 'base64'} here and you will be good to go.

One possible problem:

"Error: Invalid base64 string"

To debug, try replacing 1st line with: var base64Str = "data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==";

Another:

An incorrect path as a logical error, runs code without error but not saving the image file as it should. Ie, if the path points to a non-existant directory, misspelled directory or a inaccessable directory.

To debug, try replacing 2nd line with var path ='./'; so it will save in the script directory. Note that '/' leads to no file saved, and an empty string leads to error "Missing mandatory arguments..."

You can use png-to-jpeg module. Assuming the 'data' is in string form :

const fs = require("fs");

const pngToJpeg = require('png-to-jpeg');
const imgStr = 'data:image/png;base64, iVBORw0KGgoAAAANSUhEUgAAAfQAAAH0CAYAAADL1t.....';

const buffer = new Buffer(imgStr.split(/,\s*/)[1],'base64');
pngToJpeg({quality: 90})(buffer).then(output => fs.writeFileSync("./some-file.jpeg", output));

You have to strip the url meta information from it, the data:image/jpeg part. (Reiterating what @CBroe said) Here is a small function to return the correct information from the input string.

var data = 'data:image/jpeg;base64,iVBORw0KGgoAAAANSUhEUgAAA..kJggg==';

function decodeBase64Image(dataString) {
  var matches = dataString.match(/^data:([A-Za-z-+\/]+);base64,(.+)$/),
    response = {};

  if (matches.length !== 3) {
    return new Error('Invalid input string');
  }

  response.type = matches[1];
  response.data = new Buffer(matches[2], 'base64');

  return response;
}

var imageBuffer = decodeBase64Image(data);
console.log(imageBuffer);
// { type: 'image/jpeg',
//   data: <Buffer 89 50 4e 47 0d 0a 1a 0a 00 00 00 0d 49 48 44 52 00 00 00 b4 00 00 00 2b 08 06 00 00 00 d1 fd a2 a4 00 00 00 04 67 41 4d 41 00 00 af c8 37 05 8a e9 00 00 ...> }

Then you can save the buffer using your above method.

fs.writeFile('test.jpg', imageBuffer.data, function(err) { ... });

BufferList is obsolete, as its functionality is now in Node core. The only tricky part here is setting request not to use any encoding:

var request = require('request').defaults({ encoding: null });

request.get('http://tinypng.org/images/example-shrunk-8cadd4c7.png', function (error, response, body) {
    if (!error && response.statusCode == 200) {
        data = "data:" + response.headers["content-type"] + ";base64," + Buffer.from(body).toString('base64');
        console.log(data);
    }
});