EclecticJohny

Even Fibonacci Numbers

January 03, 2020 • ☕️ 1 min read

Project Euler: Problem 2

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.

const solutionTwo = () => {
    const upperLimit = 4000000;
    let fibonacciArray = [1, 2];
    for (
        let i = 3;
        i <= upperLimit;
        i += fibonacciArray[fibonacciArray.length - 2]
    ) {
        fibonacciArray.push(i);
    }
    return fibonacciArray.reduce((a, b) => (b % 2 === 0 ? a + b : a + 0), 0);
};