Node.js Buffer.byteLength() Method

The Buffer.byteLength() method is used to return the length in bytes of the specified buffer object. 

Syntax:

Buffer.byteLength( string, encoding )

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

• String It is a required parameter and is used to specify the object to calculate the length of the buffer. The supported types of strings are String, Buffer, TypedArray, DataView and ArrayBuffer.
• Encoding: It is an optional parameter. If the object is a string, this parameter specifies its encoding scheme. The Default value of encoding scheme is "utf8".

Return Value: It returns the number of bytes of the specified object. 

Example 1: 

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

// Create a buffer
const buf = Buffer.alloc(20);

// Check the length of a buffer object:
const lenobj = Buffer.byteLength(buf);

console.log(lenobj);

Output:

20

Example 2: 

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

// Check the length of a buffer object:
const len = Buffer.byteLength('GeeksForGeeks');

console.log(len);

Output:

13

Note:

• In Node.js v7.0.0, an invalid input parameter will throw an error.
• In Node.js v5.10, the value of the string parameter can be any TypedArray, DataView, or ArrayBuffer.
• This method is added to node.js v0.1.90.

Reference: https://nodejs.org/docs/latest-v11.x/api/buffer.html#buffer_class_method_buffer_bytelength_string_encoding