Edit in JSFiddle

//菲波那契数列
var fibonaccia = (function () {
    var storage = [0, 1];
    var f = function (n) {
        var result = storage[n];
        if (typeof result !== 'number') {
            result= f(n - 1) + f(n - 2);
            //缓存结果大大提升效率
            storage.push(result);
        }
        return result;
    }
    return f;
})();
var result=fibonaccia(20);
alert(result)