Instances of the Fibonacci Sequence

Create a function that takes a number as an argument and returns n instances of the Fibonacci sequence as an array.

Fibonacci numbers: F(n) = F(n-1) + F(n-2) with F(0) = 0 and F(1) = 1. So the easy explanation is: The next element is the sum of the two previous elements.

If you want to read more about this sequence, take a look at the On-Line Encyclopedia of Integer Sequences. Fibonacci numbers are strongly related to the golden ratio. See the OEIS and Wikipedia links in the resources tab.

Examples

fibSeq(4) ➞ [0, 1, 1, 2]

fibSeq(7) ➞ [0, 1, 1, 2, 3, 5, 8]

fibSeq(0) ➞ []

Notes

If 0 is given, return an empty array.
If no argument is given, return undefined.
The input will never be a negative integer.

Answer (1)

const fibonacci = n => (n <= 1 ? n : fibonacci(n – 1) + fibonacci(n – 2));

const fibSeq = length =>
  typeof length !== ‘number‘
    ? undefined
    : Array.from({ length }, (_, i) => fibonacci(i));

Answer (2)

const fibSeq = end => {
  if(end === 0) return [];
  else if(end === 1) return [0];
  else if(end > 1){
      let arr = Array.from({length: end});
      arr[0] = 0; arr[1] = 1;
      for(let i = 2; i < arr.length; i++){
        arr[i] = arr[i – 1] + arr[i – 2];
      }
      return arr;
  }
  return undefined;
}

Answer (3)

function fibSeq(end) {
  let fibArr = []
  let lastNum = 0, sum = 1, temp;
  while (end > 0){
      temp = sum
      sum = lastNum + sum
      fibArr.push(lastNum)
      lastNum = temp
      end— 
  } 
  return end>=0 ? fibArr : undefined
}

Answer (4)

function fibSeq(end) {
  if (end === 0) return [];
  if (!end) return undefined;
  let fib = [0, 1];
    for (i = 2; i < end; i++){
        fib[i] = fib[i – 2] + fib[i – 1];
    }
  return end === 1 ? fib.slice(0, 1) : fib
}

Answer (5)

function fibSeq(end = null) {
let [sequence, index, a, b] = [[], 0, 0, 1];
while (index < end) {
sequence.push(a);
[a, b] = [b, a + b];
index++;
}
return end === null ? undefined : sequence;
}

Answer (6)

function fibSeq(end) {
   if (end === undefined) return undefined; 
      const fibArr = [];   
      const fibNum = (num) => fibArr[num – 1] + fibArr[num – 2];   
      for (let i = 0; i < end; i++) {   
         i <= 1 ? fibArr.push(i) : fibArr.push(fibNum(i));   
      }
   return fibArr;
}
   

Answer (7)

function fibSeq(end) {
if (end === undefined) return undefined;
 
const fibArr = [];
const fibNum = (num) => fibArr[num – 1] + fibArr[num – 2];
for (let i = 0; i < end; i++) {
i <= 1 ? fibArr.push(i) : fibArr.push(fibNum(i));
}
 
return fibArr;
}

Answer (8)

function fibSeq(num) {
   let result = [];
   let first = 0;
   let second = 1;   
   for (let i = 0; i < num; i++) {
      if (i <= 1) {
         result.push(i);
      } else {
         let next = first + second;
         first = second;
         second = next;
         result.push(next);
      }
   }
   return result;
}

Answer (9)

function fibSeq(n) {
   let arr = [0, 1];
   for (let i = 2; i < n; i++){
      arr.push(arr[i–1] + arr[i–2]);
   }
   return arr.slice(0,n);
}

Answer (10)

function fibSeq(n) {
   if (n === 0) return []
   let fibArr = [0, 1]
   while (fibArr.length < n) {
      fibArr.push(fibArr[fibArr.length – 1] + fibArr[fibArr.length – 2])
   }
   return fibArr
}