# Computing a Fibonacci Sequence

date

May 30, 2021

slug

computing a-fibonacci-sequence

status

Published

summary

remember the recursion, how it works and how to spell it.

tags

Coding

type

Post

"Write a function to return an n element in Fibonacci sequence” is one of the most common questions. I'll list two methods below.

Input: A array with first two initials, the total length of the sequence,

Output: The whole sequence

Use while loop:

```
const fibonacci = (arr, length) => {
let num1 = arr[0]
let num2 = arr[1]
let next = num1 + num2
let count = 2
while (count < length) {
next = num1 + num2
num1 = num2
num2 = next
count++
arr.push(next)
}
return arr
}
```

Use recursion:

```
const fibonacci = (arr, length) => {
if (arr.length >= length) return arr
const next = arr[arr.length - 2] + arr[arr.length - 1]
arr.push(next)
return fibonacci(arr, length) // don't forget to return the function itself
}
```