var that = this;
var a = 1;
var b = 0;
var sum = 0;

// Generate Fibonacci series
// We're basically flip flopping the values of
// a & b to store our previous terms for the next round
function fib(a, b) {

	c = a + b;

	if (a > b) {
		that.b = c;
	} else {
		that.a = c;
	}

	return c;
}

// Now recurse through the Fibonacci sequence up to 4,000,000
// and get the sum of all the even numbered terms
function getFib() {

	f = fib(that.a, that.b);

	if (f < 4000000) {
		if ((f % 2) === 0) {
			that.sum = that.sum + f;
		}

		that.getFib();
	}
}

getFib(); // Start

document.writeln(sum); // Output