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freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/sum-all-odd-fibonacci-numbers/index.md

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---
title: Sum All Odd Fibonacci Numbers
---
![:triangular_flag_on_post:](https://forum.freecodecamp.com/images/emoji/emoji_one/triangular_flag_on_post.png?v=3 ":triangular_flag_on_post:") Remember to use <a>**`Read-Search-Ask`**</a> if you get stuck. Try to pair program ![:busts_in_silhouette:](https://forum.freecodecamp.com/images/emoji/emoji_one/busts_in_silhouette.png?v=3 ":busts_in_silhouette:") and write your own code ![:pencil:](https://forum.freecodecamp.com/images/emoji/emoji_one/pencil.png?v=3 ":pencil:")
### ![:checkered_flag:](https://forum.freecodecamp.com/images/emoji/emoji_one/checkered_flag.png?v=3 ":checkered_flag:") Problem Explanation:
You will need to gather all the **Fibonacci** numbers and then check for the odd ones. Once you get the odd ones then you will add them all. The last number should be the number given as a parameter if it actually happens to be an off Fibonacci number.
#### Relevant Links
* <a href='https://en.wikipedia.org/wiki/Fibonacci_number' target='_blank' rel='nofollow'>Fibonacci number</a>
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 1
To get the next number of the series, you need to add the current one to the previous and that will give you the next one.
> _try to solve the problem now_
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 2
To check if a number is even all you have to check is if `number % 2 == 0`.
> _try to solve the problem now_
## ![:speech_balloon:](https://forum.freecodecamp.com/images/emoji/emoji_one/speech_balloon.png?v=3 ":speech_balloon:") Hint: 3
As you get the next odd one, don't forget to add it to a global variable that can be returned at the end. `result += currNumber;` will do the trick.
> _try to solve the problem now_
## Spoiler Alert!
![warning sign](//discourse-user-assets.s3.amazonaws.com/original/2X/2/2d6c412a50797771301e7ceabd554cef4edcd74d.gif)
**Solution ahead!**
## ![:beginner:](https://forum.freecodecamp.com/images/emoji/emoji_one/beginner.png?v=3 ":beginner:") Basic Code Solution:
function sumFibs(num) {
var prevNumber = 0;
var currNumber = 1;
var result = 0;
while (currNumber <= num) {
if (currNumber % 2 !== 0) {
result += currNumber;
}
currNumber += prevNumber;
prevNumber = currNumber - prevNumber;
}
return result;
}
// test here
sumFibs(4);
![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://repl.it/CLnV/0' target='_blank' rel='nofollow'>Run Code</a>
### Code Explanation:
* Create a variable to keep record of the current and previous numbers along with the result that will be returned.
* Use a while loop to make sure we do not go over the number given as parameter.
* We use the modulo operand to check if the current number is odd or even. If it is even, add it to the result.
* Complete the Fibonacci circle by rotating getting the next number and swapping values after.
* Return the result.
#### Relevant Links
* <a>JS while Loop</a>
## ![:sunflower:](https://forum.freecodecamp.com/images/emoji/emoji_one/sunflower.png?v=3 ":sunflower:") Intermediate Code Solution:
function sumFibs(num) {
// Perform checks for the validity of the input
if (num < 0) return -1;
if (num === 0 || num === 1) return 1;
// Create an array of fib numbers till num
const arrFib = [1, 1];
let nextFib = 0;
[NEW] A clearer, more readable return statement (#35565) * A clearer, more readable return statement Use .filter() to get the odd values in array. Use .reduce() to sum. Two separate tasks, one line, easier to read and understand. Updated comments and Code Explanation accordingly.
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// We put the new Fibonacci numbers to the front so we
// don't need to calculate the length of the array on each
// iteration
while((nextFib = arrFib[0] + arrFib[1]) <= num) {
arrFib.unshift(nextFib);
}
[NEW] A clearer, more readable return statement (#35565) * A clearer, more readable return statement Use .filter() to get the odd values in array. Use .reduce() to sum. Two separate tasks, one line, easier to read and understand. Updated comments and Code Explanation accordingly.
2019-04-12 21:29:47 +09:00
// We filter the array to get the odd numbers and reduce them to get their sum.
return arrFib.filter(x => x % 2 != 0).reduce((a, b) => a + b);
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}
// test here
sumFibs(4);
Fix "hint" code not working for the challenge: "Sum All Odd Fibonacci Numbers" (#28676) * Fix code not passing on challenge tests The code was not passing the challenge tests because we must sum only odd numbers. Cince we didn't provided an initial value for reduce, it would use the first element of the array, and if it was an odd number, it would skip our validation and add it to the final result. [https://www.freecodecamp.org/forum/t/sum-all-odd-fibonacci-numbers-solution-not-passing-all-tests/236058](https://www.freecodecamp.org/forum/t/sum-all-odd-fibonacci-numbers-solution-not-passing-all-tests/236058) * Same English fixed for Arabic * Same English fix for Chinese * Same English fix for Portuguese * Same English fix for Russian * Same English fix for Spanish
2019-02-12 21:54:53 -02:00
![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") <a href='https://repl.it/repls/ImpassionedFineConnection' target='_blank' rel='nofollow'>Run Code</a>
fix: change directory structure
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### Code Explanation:
* Create an array of fibonacci numbers till **num**.
[NEW] A clearer, more readable return statement (#35565) * A clearer, more readable return statement Use .filter() to get the odd values in array. Use .reduce() to sum. Two separate tasks, one line, easier to read and understand. Updated comments and Code Explanation accordingly.
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* Use `filter()` method to filter out even numbers.
* Use `reduce()` method to sum the remaining (odd) values.
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* Return the sum.
#### Relevant Links
* <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-push/14298' target='_blank' rel='nofollow'>JS Array Prototype Push</a>
* <a href='http://forum.freecodecamp.com/t/javascript-for-loop/14666s-Explained' target='_blank' rel='nofollow'>JS For Loops Explained</a>
[NEW] A clearer, more readable return statement (#35565) * A clearer, more readable return statement Use .filter() to get the odd values in array. Use .reduce() to sum. Two separate tasks, one line, easier to read and understand. Updated comments and Code Explanation accordingly.
2019-04-12 21:29:47 +09:00
* <a href='https://www.freecodecamp.org/forum/t/javascript-array-prototype-filter/14289' target='_blank' rel='nofollow'>JS Array Prototype Filter</a>
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* <a href='http://forum.freecodecamp.com/t/javascript-array-prototype-reduce/14299' target='_blank' rel='nofollow'>JS Array Prototype Reduce</a>
[NEW] A clearer, more readable return statement (#35565) * A clearer, more readable return statement Use .filter() to get the odd values in array. Use .reduce() to sum. Two separate tasks, one line, easier to read and understand. Updated comments and Code Explanation accordingly.
2019-04-12 21:29:47 +09:00
fix: change directory structure
2018-10-12 15:37:13 -04:00
## ![:clipboard:](https://forum.freecodecamp.com/images/emoji/emoji_one/clipboard.png?v=3 ":clipboard:") NOTES FOR CONTRIBUTIONS:
* ![:warning:](https://forum.freecodecamp.com/images/emoji/emoji_one/warning.png?v=3 ":warning:") **DO NOT** add solutions that are similar to any existing solutions. If you think it is **_similar but better_**, then try to merge (or replace) the existing similar solution.
* Add an explanation of your solution.
* Categorize the solution in one of the following categories — **Basic**, **Intermediate** and **Advanced**. ![:traffic_light:](https://forum.freecodecamp.com/images/emoji/emoji_one/traffic_light.png?v=3 ":traffic_light:")
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