How To Print Fibonacci Sequence In JavaScript?

If you’re given an integer n, how do you print the Fibonacci sequence up to n in JavaScript?

First of all, since there are varying understanding of Fibonacci sequence, in this case we’ll assume that the 0th number is 0, 1st number is 1 and the next numbers are the sum of the previous 2 numbers.

For example, if the n is 10, we’ll print form 0th number to 10th number, resulting in [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55].


function printFibonacci(n) {
    let sequence = [];
    for (let i = 0; i <= n; i ++) {
        if (i == 0) sequence.push(0);
        else if (i == 1) sequence.push(1);
        else {
            sequence.push(sequence[sequence.length-1] + sequence[sequence.length-2]);
    return sequence;

console.log(printFibonacci(10)); //[0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]

With this code, we’re essentially iterating from 0 to n adding 0 and 1 as 0th and 1st number respectively. Then for the next numbers, we’ll be taking the sum of the last 2 numbers and repeating it until we reach the nth number.

Time Complexity : O(n)

We are iterating n times so are complexity matches our number of inputs.

Space Complexity : O(n)

We’re using an array to store our answer and the array grows accordingly to n.


That’s how you can print a sequence of Fibonacci numbers. Quite simple, right?

You’re essentially printing numbers by summing up the last 2 numbers.

For a similar tutorial about Fibonacci numbers, you can check out my post on How To Get nth Fibonacci Number in JavaScript?

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If you have a better solution be it code-wise or efficiency-wise, please do comment below!

Check out the rest of my blog for more helpful contents on Data Structures and Algorithms in JavaScript!

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