Cached Javascript Fibonacci numbers

fib.js

var fibCache = [0, 1];
 
var yourself = {
    fibonacci : function(n) {
        if (n <= 1) {
            return n;
        }
        if (!fibCache[n]) {
            fibCache[n] = this.fibonacci(n - 1) +
                this.fibonacci(n - 2);
        }
        return fibCache[n];
    }
};