Even Fibonacci numbers

by Daniel Lamb

HTML

<h1 id="answer"></h1>

JavaScript

var fibonacci = (function () {
    var memo = [0, 1];
    var fib = function (n) {
        var result = memo[n];
        if (typeof result !== 'number') {
            result = fib(n-1) + fib(n-2);
            memo[n] = result;
        }
        return result;
    };
    return fib;
}());

var result = 0, sum = 0;
for (var i = 0; result < 4000000; i += 1) {
    result = fibonacci(i);
    if(result % 2 == 0) {
        sum += result;
    }
}
document.getElementById('answer').innerHTML = sum;