Fibonacci using recursion and iteration

fibs.js

// These functions assume that fib(0) = 0, fib(1) = 1
// In other words, 0 and 1 are the seeds of the sequence.

function recursiveFib(n) {
    if(n < 0) {
        throw "Negative numbers are not allowed.";
    }
    
    if(n < 2) {
        return n;
    }

    return recursiveFib(n - 1) + recursiveFib(n - 2);
}

function iterativeFib(n) {
    var fibs = [0, 1, 1],
        i = 0;

    if(n < 0) {
        throw "Negative numbers are not allowed.";
    }
    
    if(n <= 2) {
        return fibs[n];
    }

    for(i = 3; i <= n; ++i) {
        fibs[i] = fibs[i - 1] + fibs[i - 2];
    }

    return fibs[n];
}

console.log("Recursive: " + recursiveFib(8));  // => 21
console.log("Iterative: " + iterativeFib(8));​  // => 21