Node.js Buffer.writeUInt8() Method

The Buffer.writeUInt8() method is an inbuilt application programming interface of class Buffer within Buffer module which is used to write values to buffer at the specified offset. The value should be a valid unsigned 8-bit integer otherwise behavior is undefined.

Syntax:

Buffer.writeUInt8( value, offset )

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

• value: The unsigned integer value that to be written into buffer.
• offset: It denotes the number of bytes to skipped before starting to write to buffer. The offset can be in range 0 <= offset <= buf.length – 1. The default value of offset is 0.

Return value: It returns the buffer with the value inserted at the specified offset.

Below examples illustrate the use of Buffer.writeUInt8() Method in Node.js:

Example 1:

// Node.js program to demonstrate the
// Buffer.writeUInt8() method

// Creating a buffer
const buf = Buffer.allocUnsafe(5);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x14, 0);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x15, 1);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x16, 4);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x17, 3);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x18, 2);

// Display the result
console.log(buf);

Output:

<Buffer 14 00 00 00 d6>
<Buffer 14 15 00 00 d6>
<Buffer 14 15 00 00 16>
<Buffer 14 15 00 17 16>
<Buffer 14 15 18 17 16>

Example 2:

// Node.js program to demonstrate the
// Buffer.writeUInt8() method

// Creating a buffer
const buf = Buffer.allocUnsafe(3);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x11, 0);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x22, 1);

// Display the buffer
console.log(buf);

// Using Buffer.writeUInt8() method
buf.writeUInt8(0x33, 2);

// Display the buffer
console.log(buf);

Output:

<Buffer 11 e7 31>
<Buffer 11 22 31>
<Buffer 11 22 33>

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_buf_writeuint8_value_offset