Node.js - Buffer.buf[index] property

---

---

In NodeJS buf[index], the index is a position in a buffer. It helps to set or return the octet value at the index position in a buffer. The values returned are individual bytes that fall in the range of 0x00 to 0xFF (hex) and 0 to 255(decimal).

If the index given to read the value in buffer is negative or greater than the buffer length, the value returned is undefined. It will also not update the value in buffer if the index is negative or greater than buffer length.

Syntax

Following is the syntax of the NodeJS Buffer buf[index] property −

Buf[index] = value

Example

In this example will create a buffer and read the value at position 5.

const buf = Buffer.from('Hello World');
console.log(buf);
console.log("The octet value at position 5 is :"+buf[5]);

Output

<Buffer 48 65 6c 6c 6f 20 57 6f 72 6c 64>
The octet value at position 5 is :32

Example

Let us use the index greater than the buffer.length.

const buf = Buffer.from('Hello World');
console.log(buf);
console.log("The octet value at position 15 is :"+buf[15]);

Output

<Buffer 48 65 6c 6c 6f 20 57 6f 72 6c 64>
The octet value at position 15 is :undefined

Example

In this example let us change the octet value at a position we need.

const buf = Buffer.from('Hello World');
buf[5] = 58;
console.log("The buffer after the octet value is changed at position 5 is :"+buf.toString());

Output

The buffer after the octet value is changed at position 5 is :Hello:World