JAVASCRIPT

nodejs atob

// If you need to convert to Base64 you could do so using Buffer:
console.log(Buffer.from('Hello World!').toString('base64'));
// Reverse (assuming the content you're decoding is a utf8 string):
console.log(Buffer.from(b64Encoded, 'base64').toString());

atob nodejs

(function () {
  "use strict";

  var atob = require('atob');
  var b64 = "SGVsbG8sIFdvcmxkIQ==";
  var bin = atob(b64);

  console.log(bin); // "Hello, World!"
}());