Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ... By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

fibonacci

/*
euler
Each new term in the Fibonacci sequence is generated by adding the previous two terms. 
By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...   

By considering the terms in the Fibonacci sequence whose values do not exceed four million, 
find the sum of the even-valued terms.
*/
  
function sumEvenFibonacciNumbers(){
  //create an acumulator and an array for fibonacci
  // start with 1 and 2
  var fibonacciNumbersCollection = [1,2], sumOfEvenFibonaccis = 2, sumOfTotalFibonaccis = 3, limit = 4000000;
  // loop while the value doesn't exceed four million
  while( fibonacciNumbersCollection[fibonacciNumbersCollection.length - 1] < limit ){  
    // push the new fibonacci
    var newSize = fibonacciNumbersCollection.length;
    var sumOfLastTwo = fibonacciNumbersCollection[newSize - 2] 
    + fibonacciNumbersCollection[newSize - 1];
    fibonacciNumbersCollection.push(sumOfLastTwo);
    // accumulate the even valued and all
    sumOfTotalFibonaccis += sumOfLastTwo;
    if( sumOfLastTwo % 2 === 0 ){ sumOfEvenFibonaccis += sumOfLastTwo; }

    console.log(fibonacciNumbersCollection);
 
  }
    return sumOfEvenFibonaccis;
}