Node.js Buffer.concat() Method

The Buffer.concat() method is used to concat all buffer objects in a given array into one buffer object. The return value of this method is also a buffer. If the length of the buffer is not provided then it is calculated from the Buffer instances in the list. 

Syntax:

Buffer.concat( list, length )

Parameters: This method accepts two parameters as mentioned above and described below:

• list: Contains the list of buffers to concat.
• length: It defines the length of the concatenated buffer. This parameter is optional.

Example 1: In this example, we will see the use of Buffer.concat() method 

javascript

// Returns a new buffer with the
// copy of the passed string
const buf1 = Buffer.from("Geeks");

// Returns another buffer with
// copy of the passed string
const buf2 = Buffer.from("for");

const buf3 = Buffer.from("Geeks");

// Creates an array of buffers
const list = [buf1, buf2, buf3];

// Concatenates all buffer objects into one buffer
const newbuff = Buffer.concat(list);

console.log("The concatenated buffer:");

// Displays the concatenated buffer
console.log(newbuff);

Output:

The concatenated buffer:
<Buffer 47 65 65 6b 73 66 6f 72 47 65 65 6b 73>

Example 2: In this example, we will see the use of the Buffer.concat() method 

javascript

// Returns a new buffer with the
// copy of the passed string
const buf1 = Buffer.from("Good");

// Returns another buffer with
// copy of the passed string
const buf2 = Buffer.from("morning");

const buf3 = Buffer.from("everyone");

// Creates an array of buffers
const list = [buf1, buf2, buf3];

// Concatenates all buffer objects
// into one buffer
const newbuff = Buffer.concat(list);

console.log("The concatenated buffer:");

// Displays the concatenated buffer
console.log(newbuff);

Output:

The concatenated buffer:
<Buffer 47 6f 6f 64 6d 6f 72 6e 69 6e 67 65 76 65 72 79 6f 6e 65>

Note: The above program will compile and run by using the node index.js command. Reference: https://nodejs.org/dist/latest-v13.x/docs/api/buffer.html#buffer_class_method_buffer_concat_list_totallength