Node.js Buffer.subarray() Method

Last Updated : 28 Apr, 2025

The buffer.subarray() method is an inbuilt application programming interface of the buffer module which is used to crop a part of array i.e. create sub-array from an array.
Syntax:

Buffer.subarray( starting_index, ending_index )

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

starting_index: This parameter specifies an integer value that denotes the starting address of the buffer from where new buffer to start. Its default value is 0.
ending_index: It specifies an integer value that denotes ending address of the buffer up to which the new buffer to be created. The default value is the length of the buffer.

Return Value: This method returns the cropped array. This buffer points to the same memory but with cropped starting and ending indices. If ending_index in the parameter is greater than buffer length then buffer length is taken as ending index.
Note: If the new buffer is modified then the same will be reflected in the original buffer as they point to the same memory.
Below examples illustrate the use of buffer.subarray() method in Node.js:
Example 1:

javascript

// Node.js program to demonstrate the   
// Buffer.subarray() method

// Allocating buffer 
const buf = Buffer.from('GeeksforGeeks', 'ascii');

// Printing original buffer
console.log("Original buffer is: " + buf);

// Cropping buffer, here starting index
// is 5 and ending index is 10
cropped_buf = buf.subarray(5, 10);

// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);
 
// Modifying cropped buffer
cropped_buf[0] = 70;  // F
cropped_buf[1] = 79;  // O
cropped_buf[2] = 82;  // R

// Printing cropped buffer
console.log("Cropped buffer after modification is: " + cropped_buf);

// Printing original buffer
console.log("Original buffer after modification is: " + buf);

Output:

Original buffer is: GeeksforGeeks
Cropped buffer is: forGe
Cropped buffer after modification is: FORGe
Original buffer after modification is: GeeksFORGeeks

Example 2:

javascript

// Node.js program to demonstrate the   
// Buffer.subarray() method

// Allocating buffer 
const buf = Buffer.from('GeeksforGeeks', 'ascii');

// Printing original buffer
console.log("Original buffer is: " + buf);
 
// Cropping buffer, here starting index
// is -10 and ending index is -1
cropped_buf = buf.subarray(-12, -1);

// Printing cropped buffer
console.log("Cropped buffer is:" + cropped_buf);
 
// Cropping buffer again, here starting
// index is -10 and ending index is -5
cropped_buf = buf.subarray(-10, -5);

// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);
 
// Cropping buffer again with no parameter
cropped_buf = buf.subarray();

// Printing cropped buffer
console.log("Cropped buffer is: " + cropped_buf);

Output:

Original buffer is: GeeksforGeeks
Cropped buffer is:eeksforGeek
Cropped buffer is: ksfor
Cropped buffer is: GeeksforGeeks

Note: The above program will compile and run by using the node index.js command.
Reference: https://nodejs.org/api/buffer.html#buffer_buf_subarray_start_end