//求斐波那契數列第n位var n = parseInt(window.prompt('輸入你要求的斐波那契數列的位數'));var first = 1,  second = 1,  third;if (n > 2) {  for (var i = 0; i < n - 2; i++) {    third = first + second;    first = second;    second = third;    document.writeln('斐波那契數列的第' + (i + 3) + '位是：' + third)  }} else {  document.writeln(1);}

 //倒序輸出 var n = window.prompt("請輸入三位數的整數"); for (var i = n.length; i >= 0; i--) {   document.writeln(n.charAt(i)); } document.writeln(a);

//判斷是否質數var count = 0; //計數器for (var i = 1; i < 100; i++) {  //看每個i是否質數  for (var j = 1; j <= i; j++) {    if (i % j == 0) {      //統計被整除的次數      count++;    }  }  //如果被整除的次數等于2次，則輸出這個數  if (count == 2) {    document.writeln(i + " ");  }  //計數器清零  count=0;}