js-斐波那切数列

f(1) = 1;

f(2) = 1;

f(3) = f(1) + f(2) = 2;

f(4) = f(3) + f(2) = 3;

f(5) = f(4) + f(3) = 5;

f(6) = f(5) + f(4) = 8;

f(n) = f(n-1) + f(n-2) ;

function fibonacci(n) {

　　if(n ==0 || n==1)

　　return n;

　　return fibonacci(n-1) + fibonacci(n-2);

}

var n_num = fibonacci(9);

console.log(n_num);