案例1：计算两个数的和

var num1 = 5;
var num2 = 10;
var sum = num1 + num2;
console.log("两个数的和是：" + sum);
 

案例2：判断一个数是否是偶数

var num = 7;
if (num % 2 === 0) {
  console.log(num + "是偶数");
} else {
  console.log(num + "是奇数");
}
 

案例3：计算数组中所有元素的平均值

var numbers = [1, 2, 3, 4, 5];
var sum = 0;
for (var i = 0; i < numbers.length; i++) {
  sum += numbers[i];
}
var average = sum / numbers.length;
console.log("平均值是：" + average);
 

案例4：找出数组中的最大值

var numbers = [2, 5, 1, 9, 3];
var max = numbers[0];
for (var i = 1; i < numbers.length; i++) {
  if (numbers[i] > max) {
    max = numbers[i];
  }
}
console.log("数组中的最大值是：" + max);
 

案例5：反转字符串

var str = "Hello World!";
var reversedStr = "";
for (var i = str.length - 1; i >= 0; i--) {
  reversedStr += str[i];
}
console.log("反转后的字符串是：" + reversedStr);
 

案例6：判断一个字符串是否是回文

var str = "level";
var reversedStr = "";
for (var i = str.length - 1; i >= 0; i--) {
  reversedStr += str[i];
}
if (str === reversedStr) {
  console.log(str + "是回文");
} else {
  console.log(str + "不是回文");
}
 

案例7：生成指定范围内的随机整数

var min = 1;
var max = 10;
var randomNum = Math.floor(Math.random() * (max - min + 1)) + min;
console.log("随机数是：" + randomNum);
 

案例8：获取当前日期和时间

var now = new Date();
console.log("当前日期和时间是：" + now);
 

案例9：将字符串转换为大写

var str = "hello world!";
var upperCaseStr = str.toUpperCase();
console.log("转换为大写后的字符串是：" + upperCaseStr);
 

案例10：计算阶乘

function factorial(num) {
  if (num === 0) {
    return 1;
  } else {
    return num * factorial(num - 1);
  }
}

var num = 5;
var result = factorial(num);
console.log(num + "的阶乘是：" + result);