斐波那契数列是以下一系列数字：
0, 1, 1, 2, 3, 5, 8, 13, 21, 34,... 在种子 0 和 1 之后，后续的每一个数字都是前面两个数字之和。
function fibonacci(n) {if (n == 0 || n == 1) {return n;}return fibonacci(n - 1) + fibonacci(n - 2);}
function fibonacci(n) {let a = (b = 1);for (let i = 3; i <= n; i++) {[a, b] = [b, a + b];}return b;}
function fibonacci(n, a = 1, b = 1) {if (n <= 1) {return b;}return fibonacci(n - 1, b, a + b);}
注:该序列是从 1 开始斐波那契数列 关于尾调用
function memo(fn) {var r = {};return function (n) {if (r[n] == undefined) {r[n] = fn(n);}return r[n];};}var fibonacci = memo(function (n) {if (n == 0 || n == 1) {return n;}return fibonacci(n - 1) + fibonacci(n - 2);});
https://segmentfault.com/a/1190000007115162 https://zhuanlan.zhihu.com/p/27205391