Base64 encoding in Cloudflare Worker

When working with Cloudflare Workers, a common task is to encode data in base64 format. Unlike Node.js environments where the Buffer class is available, Cloudflare Workers require a different approach since Buffer is not present.

Using btoa for Base64 Encoding

The btoa function, which stands for binary-to-ASCII, is a standard JavaScript function available in most JavaScript environments, including Cloudflare Workers. It encodes a string in base64 format. Here’s how you can use it:

function encodeBase64(str) {
    return btoa(unescape(encodeURIComponent(str)));
}

const data = "Hello, world!";
const encodedData = encodeBase64(data);
console.log(encodedData); // Outputs base64 encoded string

In this code snippet, encodeURIComponent is used to encode the string as a URI component, and unescape is used to get a Unicode string. This prepares the string for encoding in base64 format with btoa.

Handling Large Strings

When encoding large strings, the approach needs to be slightly different to avoid the ‘Maximum call stack size exceeded’ error. This error typically occurs in JavaScript when a function calls itself too many times (recursion) or when using the spread syntax (...) on a large array. To handle large strings safely, use the reduce method combined with String.fromCharCode to convert the encoded data to a string:

function encodeBase64(str) {
  const encoder = new TextEncoder();
  const encoded = encoder.encode(str);
  
  const binaryString = encoded.reduce((acc, byte) => {
    return acc + String.fromCharCode(byte);
  }, '');

  return btoa(binaryString);
}

This method efficiently handles larger strings without exceeding the call stack size, making it a more robust solution for base64 encoding in Cloudflare Workers.