The **`buf.indexof()` function** takes a value and returns the index of where that value first occured in the buffer.

The `buf.indexOf()` function accepts three parameters:
* **`value`**: The `buf.indexOf()` function returns the first occurrence of `value` in the buffer (`buf`). `value` can be of type `string`, `buffer`,`integer`, and `Uint8Array`.
* **`byteoffset`**: Indicates where to begin the search in the buffer (`buf`), and is set to 0 by default. If `byteoffset` is negative, it is set to the end of the buffer (`buf`).  `byteoffset` is of type `integer`.
* **`encoding`**: Determines the binary representation of the `value` if it is of type `string`. `encoding` is set to `utf-8` by default.


The `buf.indexOf()` function returns an integer indicating the index at which the `value` lies in the buffer (`buf`), and returns -1 if the `value` does not exist in `buf`.

>**Note**: The program will throw a `TypeError` if `value` is not a string, buffer, or integer.

# Examples
The following code demonstrates how to use the `Buffer.indexOf()` function in Node.js.

// create a buffer
var buf = Buffer.from("Educative.io")
//call the indexOf() function
console.log(buf.indexOf('e'))
// set the offset to the 4th byte
console.log(buf.indexOf('i',4))
//input the ascii value of c
console.log(buf.indexOf(99))
//input an out of range number. 97 is the ascii of a.
console.log(buf.indexOf(97+256))
//input the value as a buffer
console.log(buf.indexOf(Buffer.from('tive.io')))


The above program applies the `buf.indexOf()` function on values of type string, buffer, and integer.
* The program calls the `indexOf()` function on a buffer created with a string and obtains the indexes of the string's characters in the buffer.
* The program then inputs an #key# integer : is treated as an ASCII value #key#, and the index of the corresponding character is returned.
* When an out-of-range ASCII value is input to the function, the program truncates the value and returns the character corresponding to the truncated value.
* The program uses another buffer to test the `indexOf()` function and returns the index from where the other buffer starts.
>**Note**: If `value` is a number outside of the range 0-255, the number is converted into a valid byte integer. If `byteoffset` is not a valid byte, it is converted into a valid byte.  The entire buffer is searched if `byteoffset` is converted to 0 or NaN.

How to use the buf.indexOf() function in Node.js

buf.indexOf() in Node.js returns the first index of a value in a buffer, handling strings, buffers, integers, and Uint8Array.

How to use the buf.indexOf() function in Node.js

Prototype

Parameters and return value

Examples