The btoa() function takes a JavaScript string as a parameter. In JavaScript strings are represented using the UTF-16 character encoding: in this encoding, strings are represented as a sequence of 16-bit (2 bytes) units.

But bota() function is not available in node js to achieve the same functionality we can use the buffer in node js.

// Try in browser console
btoa('Hello india') // "SGVsbG8gaW5kaWE="

The same result we can achieve with the help of node Js buffer.

Buffer.from('Hello india').toString('base64') // SGVsbG8gaW5kaWE=

What is buffer?

A buffer is an area of memory. It represents a fixed-size chunk of memory (can’t be resized) allocated outside of the V8 JavaScript engine. You can think of a buffer like an array of integers, which each represent a byte of data.

Buffers were introduced to help developers deal with binary data, in an ecosystem that traditionally only dealt with strings rather than binaries.

How to create a buffer

A buffer is created using the Buffer.from(), Buffer.alloc(), and Buffer.allocUnsafe() methods.

Access the content of a buffer

A buffer, being an array of bytes, can be accessed like an array:

const buf = Buffer.from('Hi !!')
console.log(buf) // <Buffer 48 69 20 21 21>
console.log(buf[0]) //72
console.log(buf[1]) //105
console.log(buf[2]) //32
console.log(buf[3]) //33

Those numbers are the UTF-8 bytes that identify the characters in the buffer (H → 72, i → 105, ! → 33). This happens because Buffer.from() uses UTF-8 by default. Keep in mind that some characters may occupy more than one byte in the buffer (é → 195 169).

You can print complete strings using toString method.

console.log(buf.toString()); // Hi !!

Get length of buffer

const buf = Buffer.from('Hi !!');
console.log(buf.length); // 5

Iterate over the contents of a buffer

const buf = Buffer.from('Hi !!')
for (const item of buf) {
  console.log(item) //72 105 32 33
}

Slice a buffer

If you want to create a partial visualization of a buffer, you can create a slice. Use the subarray() method to create it. The first parameter is the starting position, and you can specify an optional second parameter with the end position.

const buf = Buffer.from('Hey!')
buf.subarray(0).toString() //Hey!
const slice = buf.subarray(0, 2)
console.log(slice.toString()) //He
buf[1] = 111 //o
console.log(slice.toString()) //Ho

Copy a buffer

Using set() method we can copy a buffer.

const buf = Buffer.from('Hi !!')
let bufcopy = Buffer.alloc(5) //allocate 5 bytes
bufcopy.set(buf)

By default, you copy the whole buffer. If you only want to copy a part of the buffer, you can use .subarray() and the offset argument that specifies an offset to write to:

const buf = Buffer.from('Hey?')
let bufcopy = Buffer.from('Moo!')
bufcopy.set(buf.subarray(1, 3), 1)
bufcopy.toString() //'Mey!'