Base64 Encode Decode in Javascript

Welcome to the Base64 Encode Decode in Javascript page! Here, you'll find the source code for this program as well as a description of how the program works.

Current Solution

#!/usr/bin/env node

function usageAndExit() {
  console.error("Usage: please provide a mode and a string to encode/decode");
  process.exit(1);
}

function isValidBase64(str) {
  // Check length multiple of 4
  if (str.length % 4 !== 0) return false;
  // Only A–Z, a–z, 0–9, +, /, = allowed
  if (!/^[A-Za-z0-9+/]*={0,2}$/.test(str)) return false;
  // = only allowed at end, at most two
  const idx = str.indexOf("=");
  if (idx !== -1 && idx < str.length - 2) {
    // e.g. “ab==cd” invalid
    return false;
  }
  return true;
}

function encodeBase64(input) {
  // Use Buffer in Node.js
  return Buffer.from(input, "ascii").toString("base64");
}

function decodeBase64(input) {
  // Validate first
  if (!isValidBase64(input)) {
    usageAndExit();
  }
  // Buffer will ignore invalid trailing bits
  return Buffer.from(input, "base64").toString("ascii");
}

function main() {
  const args = process.argv.slice(2);
  if (args.length < 2) {
    usageAndExit();
  }
  const mode = args[0];
  const text = args[1];

  if (!text) {
    usageAndExit();
  }

  if (mode === "encode") {
    console.log(encodeBase64(text));
  } else if (mode === "decode") {
    console.log(decodeBase64(text));
  } else {
    usageAndExit();
  }
}

if (require.main === module) {
  main();
}

Base64 Encode Decode in Javascript was written by:

• Eshaan Walia

If you see anything you'd like to change or update, please consider contributing.

How to Implement the Solution

No 'How to Implement the Solution' section available. Please consider contributing.

How to Run the Solution

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