1.if和switch语句
1.1 if 语句
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>年份判断</title>
</head>
<body>
<script>
var year = prompt("请输入年份：");
if ((year % 4 == 0 && year % 100 != 0) || year % 400 == 0) {
alert("您输入的闰年");
} else {
alert("您输入的是平年");
}
</script>
</body>
</html>
1.2if分支： if 和 else if
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>成绩</title>
</head>
<body>
<script>
// 必须安装从小到大的顺序来写
var score = prompt("请输入分数");
if (score >= 90) {
alert("你真棒");
} else if (score >= 80) {
alert("很不错");
} else if (score >= 70) {
alert("一般般");
} else if (score >= 60) {
alert("要加油了");
} else {//A儿死
alert("回家种地吧");
}
</script>
</body>
</html>
1.3三元表达式 ‘？’ ‘：’
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>倒计时</title>
</head>
<body>
<script>
var time = prompt("请输入0~59的一个数字");
var result = time < 10 ? "0" + time : time;
alert(result);
</script>
</body>
</html>
1.4 switch 语句：switch case break default
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>水果价格</title>
</head>
<body>
<script>
var sg = prompt("请输入您查询的水果");
switch (sg) {
case "榴莲":
alert("35一斤");
break;
case "香蕉":
alert("3.5一斤");
break;
case "苹果":
alert("4.5一斤");
break;
default:
alert("没有此水果");
}
</script>
</body>
</html>
总结
作业1
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>判断时间</title>
</head>
<body>
<script>
var time = prompt("请输入时间");
if (time <= 12) {
alert("中午好");
} else if (time <= 18) {
alert("傍晚好");
} else if (time <= 23) {
alert("深夜好");
}
</script>
</body>
</html>
作业2
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>输入一个数，比较大小</title>
</head>
<body>
<script>
var sz1 = prompt("请您输入一个数字");
var sz2 = prompt("请您输入一个数字");
if (sz1 >= sz2) {
alert(sz1 + "是最大的");
} else if(sz1 <= sz2) {
alert(sz2 + "是最大的");
}
</script>
</body>
</html>
作业3
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>判断数的奇偶性</title>
</head>
<body>
<script>
var sz = prompt("请您输入一个数字");
if (sz % 2 == 0) {
alert("这是一个偶数");
} else {
alert("这是一个奇数");
}
</script>
</body>
</html>
作业4
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<script>
var week = prompt("请输入星期几");
switch (week) {
case "礼拜一":
alert("今天是礼拜一");
break;
case "礼拜二":
alert("今天是礼拜二");
break;
case "礼拜三":
alert("今天是礼拜三");
break;
case "礼拜四":
alert("今天是礼拜四");
break;
case "礼拜五":
alert("今天是礼拜五");
break;
case "礼拜六":
alert("今天是礼拜六");
break;
case "礼拜天":
alert("今天是礼拜天");
break;
default:
alert("您输入错误");
}
</script>
</body>
</html>
作业5
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<script>
var money = prompt("本次收集的班费是多少元");
if (money >= 2000) {
alert("请大家吃西餐");
} else if (2000 > money&& money>= 1500) {
alert("请大家吃快餐");
} else if (1500 > money&& money >= 1000) {
alert("请大家喝饮料");
} else if (1000 > money) {
alert("下次把钱带够");
}
</script>
</body>
</html>
作业6
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
</head>
<body>
<script>
var grade = prompt("请输入您本次的成绩");
if (grade > 90) {
alert("你的评级为A");
} else if (grade > 80) {
alert("你的评级为B");
} else if (grade > 70) {
alert("你的评级为C");
} else if (grade >= 60) {
alert("你的评级为D");
} else if (grade <= 60) {
alert("你的评级为E");
}
</script>
</body>
</html>
