freeCodeCamp/curriculum/challenges/english/99-dev-playground/daily-coding-challenges-javascript/javascript-challenge-3.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
681cb1a2dab50c87ddb2e514	JavaScript Challenge 3: Fibonacci Sequence	28	javascript-challenge-3

--description--

The Fibonacci sequence is a series of numbers where each number is the sum of the two preceding ones. When starting with 0 and 1, the first 10 numbers in the sequence are 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.

Given an array containing the first two numbers of a Fibonacci sequence, and an integer representing the length of the sequence, return an array containing the sequence of the given length.

• Your function should handle sequences of any length greater than or equal to zero.
• If the length is zero, return an empty array.
• Note that the starting numbers are part of the sequence.

--hints--

fibonacciSequence([0, 1], 20) should return [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181].

assert.deepEqual(fibonacciSequence([0, 1], 20), [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181]);

fibonacciSequence([21, 32], 1) should return [21].

assert.deepEqual(fibonacciSequence([21, 32], 1), [21]);

fibonacciSequence([0, 1], 0) should return [].

assert.deepEqual(fibonacciSequence([0, 1], 0), []);

fibonacciSequence([10, 20], 2) should return [10, 20].

assert.deepEqual(fibonacciSequence([10, 20], 2), [10, 20]);

fibonacciSequence([123456789, 987654321], 5) should return [123456789, 987654321, 1111111110, 2098765431, 3209876541].

assert.deepEqual(fibonacciSequence([123456789, 987654321], 5), [123456789, 987654321, 1111111110, 2098765431, 3209876541]);

--seed--

--seed-contents--

function fibonacciSequence(startSequence, length) {

  return length;
}

--solutions--

function fibonacciSequence(startSequence, length) {
  if (length === 0) return [];
  if (length === 1) return [startSequence[0]];
  if (length === 2) return [...startSequence];

  const sequence = [...startSequence];
  while (sequence.length < length) {
    const nextValue = sequence[sequence.length - 1] + sequence[sequence.length - 2];
    sequence.push(nextValue);
  }
  return sequence;
}