Let me guess. You’re managing I/O activities and encountered this error? What happened is either:

You’re using the Buffer class in a browser environment. Only Node.js, a server-side JavaScript runtime environment, offers the Buffer class. This error will appear if you attempt to use the Buffer class in a browser.
The Buffer class is not supported by the version of Node.js you are running. The later versions of Node.js (4.x) included the Buffer class. The ReferenceError: Buffer is not defined error could appear if you are using an older version of Node.js.

In Node.js, a buffer containing unprocessed binary data is represented by a global object called Buffer. For operations like reading from or writing to files, managing network packets, and encoding and decoding data, the ability to store and interact with binary data is quite useful. Therefore, when you attempt to use the Buffer class in Node.js but it is not available, ReferenceError: Buffer is not defined occurs.

Example of “ReferenceError: Buffer is not defined”

<!DOCTYPE html>
<html>
<head>
    <title>Buffer in Browser</title>
</head>
<body>
    <script>
        try {
            const data = 'Hello, Browser!';
            const bufferData = Buffer.from(data);

            console.log(bufferData);
        } catch (error) {

            console.error(error);
        }
    </script>
</body>
</html>

Now, the ReferenceError: Buffer is not defined error will be logged to the browser's developer console when you access this HTML file in a web browser. This is due to the fact that the Buffer class is exclusive to Node.js and is not accessible in a typical browser setting.

Output:

ReferenceError: Buffer is not defined
   at example.html:11:32
(anonymous) @example.html:16

How to resolve the “ReferenceError: Buffer is not defined” error

You can use the below strategies to resolve the error:

Node.js version upgrade: If you are still using Node.js version 4 or earlier, think about upgrading to a newer version.
Buffer object usage: The Buffer object must be explicitly mentioned before use in later versions of Node.js, i.e. 4 and beyond, in order to avoid an error.
Run the script using Node.js: This is recommended rather than through the browser.
Buffer.from() method usage: It’s best to use the Buffer.from() method in recent versions of Node.js instead of the Buffer constructor to generate a new Buffer object because it’s more effective and flexible and can create a new Buffer object from a variety of sources.

For example:
```
// Use Buffer.from() to create a Buffer object
const myBuffer = Buffer.from('Hello, Node.js');
console.log(myBuffer.toString());
```

If you work with binary data, there’s no other way around it

The Buffer object must be required at the beginning of your Node.js script in order to fix this mistake. You should also try using Buffer.from() to create Buffer objects in more recent Node.js versions.

Simply put, to avoid the ReferenceError: Buffer is not defined error in Node.js, you need to run the script with Node.js rather than in the browser. If that doesn’t work, double-check you explicitly mentioned the Buffer object before use. If that still doesn’t work, try upgrading to the latest version of Node.js as it sounds like you have an old version.

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