function createRec(callback, cache) {
    cache = cache || [];

    var rec = function(n) {
　　　　(n in cache) || (cache[n] = callback(rec, n));
           return cache[n];
    }

　　return rec;
}

var fib = createRec(function(cal, n) {
    return cal(n - 1) + cal(n - 2);
}, [0, 1, 1]);

function fibonacci(n) {// author黄雪良
     return n <= 2 ? 1 : fibonacci(n - 1) + fibonacci(n - 2);
}

function fibonacci(n, ret1, ret2) {
    if (n < 2) {
        return ret1;
    }
    return fibonacci(n - 1, ret2, ret1 + ret2);
}