1、阶乘求和：4的阶乘是1*2*3*4
<script>
function jiechen(value) {
var n = 1;
for (var i = 1; i <= value; i++) {
n *= i;
}
return n;
}
function sum(value) {
var n = 0;
for (var i = 1; i <= value; i++) {
n += jiechen(i);
}
return n;
}
console.log(sum(3));//9
</script>
2、素数：又称质数，除了1和它本身，不能被其他数整除
<script>
function isPrime(num) {
for (var i = 2; i < num; i++) {
if (num % i === 0) {
return false;
}
}
return true;
}
console.log(isPrime(9));//false
</script>
3、将1-10中的奇数放入数组
<script>
var arr = [];
for (var i = 1; i <= 10; i++) {
if (i % 2 !== 0) {
arr[arr.length] = i;
}
}
console.log(arr);//[1, 3, 5, 7, 9]
</script>
4、将1-10中的偶数放入数组
<script>
var arr = [];
for (var i = 1; i <= 10; i++) {
if (i % 2 === 0) {
arr[arr.length] = i;
}
}
console.log(arr);//[2, 4, 6, 8, 10]
</script>
5、数组翻转
<script>
var arr = ["刘备", "关羽", "张飞", "诸葛亮", "马超", "黄忠", "姜维"];
console.log(arr);
var newArr = [];
for (var i = 0; i < arr.length; i++) {
newArr[newArr.length] = arr[arr.length - 1 - i];//用新数组的长度作为索引值。
}
console.log(newArr);
</script>
<script>
var arr = ["刘备", "关羽", "张飞", "诸葛亮", "马超", "黄忠", "姜维"];
console.log(arr);
var newArr = [];
for (var i = 0; i < arr.length / 2; i++) {
var temp = arr[i];
arr[i] = arr[arr.length - 1 - i];//前面项和对应的后面项交换位置。（arr.length-1-i = 倒数第i+1项）
arr[arr.length - 1 - i] = temp;
}
console.log(arr);
</script>
5、递归法计算1-100的值
<script>
function getSum(n) {
if (n < 1) {
return 0;
}
return n + getSum(n - 1);
}
console.log(getSum(100));//5050
</script>
6、斐波那契数列：1、1、2、3、5、8、13、21、34、…
<script>
var n1 = 1;
var n2 = 1;
function getNum(num) {
for (var i = 3; i <= num; i++) {
var temp = n2;
n2 = n1 + n2;
n1 = temp;
}
return n2;
}
console.log(getNum(6));//8
</script>
7、判断闰年：四年一闰而且百年不闰或者四百年一润
<script>
function isRun(year) {
if (year % 4 === 0 && year % 100 !== 0 || year % 400 === 0) {
return true;
}
return false;
}
</script>
8、输入年月日，计算这天是当年的第多少天
<script>
function isRun(year) {
if (year % 4 === 0 && year % 100 !== 0 || year % 400 === 0) {
return true;
}
return false;
}
function getDay(year, month, day) {
var arr = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
for (var i = 0; i < month - 1; i++) {
day = day + arr[i];
}
if (month > 2 && isRun(year)) {
day++;
}
return day;
}
console.log(getDay(2017,3,17));//76
</script>