In Node.js, the Buffer module is used to handle binary data. The Buffer module is within the global scope, which means that Buffer objects can be accessed anywhere in the environment without importing the module with require().

A Buffer object represents a fixed amount of memory that can’t be resized. Buffer objects are similar to an array of integers where each element in the array represents a byte of data. The buffer object will have a range of integers from 0 to 255 inclusive.

The Buffer module provides a variety of methods to handle the binary data such as .alloc(), .toString(), .from(), and .concat().

The .alloc() method creates a new Buffer object with the size specified as the first parameter. .alloc() accepts three arguments:

• Size: Required. The size of the buffer
• Fill: Optional. A value to fill the buffer with. Default is 0.
• Encoding: Optional. Default is UTF-8.

const buffer = Buffer.alloc(5);
console.log(buffer); // Ouput: [0, 0, 0, 0, 0]

The .toString() method translates the Buffer object into a human-readable string. It accepts three optional arguments:

• Encoding: Default is UTF-8.
• Start: The byte offset to begin translating in the Buffer object. Default is 0.
• End: The byte offset to end translating in the Buffer object. Default is the length of the buffer. The start and end of the buffer are similar to the start and end of an array, where the first element is 0 and increments upwards.

const buffer = Buffer.alloc(5, 'a');
console.log(buffer.toString()); // Output: aaaaa

The .from() method is provided to create a new Buffer object from the specified string, array, or buffer. The method accepts two arguments:

• Object: Required. An object to fill the buffer with.
• Encoding: Optional. Default is UTF-8.

const buffer = Buffer.from('hello');
console.log(buffer); // Output: [104, 101, 108, 108, 111]

The .concat() method joins all buffer objects passed in an array into one Buffer object. .concat() comes in handy because a Buffer object can’t be resized. This method accepts two arguments:

• Array: Required. An array containing Buffer objects.
• Length: Optional. Specifies the length of the concatenated buffer.

const buffer1 = Buffer.from('hello'); // Output: [104, 101, 108, 108, 111]
const buffer2 = Buffer.from('world'); // Output:[119, 111, 114, 108, 100]
const array = [buffer1, buffer2];
const bufferConcat = Buffer.concat(array);

console.log(bufferConcat); // Output: [104, 101, 108, 108, 111, 119, 111, 114, 108, 100]