--- 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 **`Read-Search-Ask`** 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 * Fibonacci number ## ![: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:") Run Code ### 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 * JS while Loop ## ![: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; // 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); } // Sum only the odd numbers and return the value return arrFib.reduce((acc, curr) => { return acc + curr * (curr % 2); }); } // test here sumFibs(4); ![:rocket:](https://forum.freecodecamp.com/images/emoji/emoji_one/rocket.png?v=3 ":rocket:") Run Code ### Code Explanation: * Create an array of fibonacci numbers till **num**. * Use `reduce()` method to find the sum of odd members of array. * Return the sum. #### Relevant Links * JS Array Prototype Push * JS For Loops Explained * JS Array Prototype Reduce ## ![: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:") * Please add your username only if you have added any **relevant main contents**. (![:warning:](https://forum.freecodecamp.com/images/emoji/emoji_one/warning.png?v=3 ":warning:") **_DO NOT_** _remove any existing usernames_) > See ![:point_right:](https://forum.freecodecamp.com/images/emoji/emoji_one/point_right.png?v=3 ":point_right:") **`Wiki Challenge Solution Template`** for reference.