freeCodeCamp/curriculum/challenges/english/02-javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/sum-all-odd-fibonacci-numbers.english.md

id, title, isRequired, challengeType

id	title	isRequired	challengeType
a5229172f011153519423690	Sum All Odd Fibonacci Numbers	true	5

Description

Given a positive integer num, return the sum of all odd Fibonacci numbers that are less than or equal to num. The first two numbers in the Fibonacci sequence are 1 and 1. Every additional number in the sequence is the sum of the two previous numbers. The first six numbers of the Fibonacci sequence are 1, 1, 2, 3, 5 and 8. For example, sumFibs(10) should return 10 because all odd Fibonacci numbers less than or equal to 10 are 1, 1, 3, and 5. Remember to use Read-Search-Ask if you get stuck. Try to pair program. Write your own code.

Instructions

Tests

tests:
  - text: <code>sumFibs(1)</code> should return a number.
    testString: 'assert(typeof sumFibs(1) === "number", ''<code>sumFibs(1)</code> should return a number.'');'
  - text: <code>sumFibs(1000)</code> should return 1785.
    testString: 'assert(sumFibs(1000) === 1785, ''<code>sumFibs(1000)</code> should return 1785.'');'
  - text: <code>sumFibs(4000000)</code> should return 4613732.
    testString: 'assert(sumFibs(4000000) === 4613732, ''<code>sumFibs(4000000)</code> should return 4613732.'');'
  - text: <code>sumFibs(4)</code> should return 5.
    testString: 'assert(sumFibs(4) === 5, ''<code>sumFibs(4)</code> should return 5.'');'
  - text: <code>sumFibs(75024)</code> should return 60696.
    testString: 'assert(sumFibs(75024) === 60696, ''<code>sumFibs(75024)</code> should return 60696.'');'
  - text: <code>sumFibs(75025)</code> should return 135721.
    testString: 'assert(sumFibs(75025) === 135721, ''<code>sumFibs(75025)</code> should return 135721.'');'

Challenge Seed

function sumFibs(num) {
  return num;
}

sumFibs(4);

Solution

function sumFibs(num) {
  var a = 1; 
  var b = 1;
  var s = 0;
  while (a <= num) {
    if (a % 2 !== 0) {   
      s += a; 
    }
    a = [b, b=b+a][0];
  }
  return s;
}