解题：假如投资的年利率为5%，试求从1000块增长到5000块，需要花费多少年？

        var money = 1000, bonus = 0.05, years = 0;

        while(money <= 5000){
            money = money*(1+bonus);
            ++years;

            console.log(money);
            console.log(years);
        }

        document.write(money+'</br>');
        document.write(years);