save base64 encoded image

base64-image-upload.js

let fs = require('fs');

// string generated by canvas.toDataURL()
let img = "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0"
    + "NAAAAKElEQVQ4jWNgYGD4Twzu6FhFFGYYNXDUwGFpIAk2E4dHDRw1cDgaCAASFOffhEIO"
    + "3gAAAABJRU5ErkJggg==";
    
// Grab the extension of the file
let ext = img.split(';')[0].match(/jpeg|png|gif/)[0];

// strip off the data: url prefix to get just the base64-encoded bytes
let data = img.replace(/^data.+base64,/, '');
let buf = new Buffer(data, 'base64');

// Write to file with the name(image + . + extension)
fs.writeFile(`image.${ext}`, buf);