function feibo(a){   if(!a || a <= 0){   throw new Error("參數錯誤，必須大于0"); }else if(a == 1){  return 1; }else if(a == 2){  return 2; }else{  return feibo(a-1) + feibo(a-2); }}console.log(feibo(7));<br><br><br><br>

function feibo(n){  if(n <= 2){   return 1;  }  var s1 = 1;  var s2 = 1;  for(var i = 3; i <= n; i++){   s2 = s2 + s1;   s1 = s2 - s1;  }  return s2; } console.log(feibo(6));