fibbonaci.js

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 fibonacci2 = function (n) {
    return n < 2 ? n : fibonacci2(n - 1) + fibonacci2(n - 2);
};


var start = new Date();

fibonacci(30);

var elapsed = new Date() - start;
console.log("fibonacci1: " + elapsed);

start = new Date();

fibonacci2(30);

elapsed = new Date() - start;
console.log("fibonacci2: " + elapsed);