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Node.js Buffer Explained

What are Buffers?

Binary is simply a set or a collection of 1 and 0. Each number in a binary, each 1 and 0 in a set are called a bit. Computer converts the data to this binary format to store and perform operations. For example, the following are five different binaries:

10, 01, 001, 1110, 00101011

JavaScript does not have a byte type data in its core API. To handle binary data Node.js includes a binary buffer implementation with a global module called Buffer.

Creating a Buffer

There are different ways you can create a buffer in Node.js. You can create an empty buffer by with a size of 10 bytes.

const buf1 = Buffer.alloc(10);

From UTF-8-encoded strings, the creation is like this:

const buf2 = Buffer.from('Hello World!');

There are different accepted encoding when creating a Buffer:

  • ascii
  • utf-8
  • base64:
  • latin1
  • binary
  • hex

There are three separate functions allocated in the Buffer API to use and create new buffers. In above examples we have seen alloc() and from(). The third one is allocUnsafe().

const buf3 = Buffer.allocUnsafe(10);

When returned, this function might contain old data that needs to be overwritten.

Interactions with Buffer

There are different interactions that can be made with the Buffer API. We are going to cover most of them here. Let us start with converting a buffer to JSON.

let bufferOne = Buffer.from('This is a buffer example.');
console.log(bufferOne);

// Output: <Buffer 54 68 69 73 20 69 73 20 61 20 62 75 66 66 65 72 20 65 78 61 6d 70 6c 65 2e>

let json = JSON.stringify(bufferOne);
console.log(json);

// Output: {"type": "Buffer", "data": [84,104,105,115,32,105,115,32,97,32,98,117,102,102,101,114,32,101,120,97,109,112,108,101,46]}

The JSON specifies that the type of object being transformed is a Buffer, and its data. Converting an empty buffer to JSON will show us that it contains nothing but zeros.

const emptyBuf = Buffer.alloc(10);

emptyBuf.toJSON();

// Output: { "type": "Buffer", "data": [ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ] }

Do notice that, Buffer API also provides a direct function toJSON() to convert a buffer into a JSON object. To examine the size of a buffer, we can use lengthmethod.

emptyBuf.length;
// Output: 10

Now let us convert buffer to a readable string, in our case, the utf-8 encoded.

console.log(bufferOne.toString('utf8'));

// Output: This is a buffer example.

.toString() by default converts a buffer to a utf-8 format string. This is how you decode a buffer. If you specify an encoding you can convert the buffer to another encoding

console.log(bufferOne.toString('base64'));

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