您的位置：首页 > Web前端 > JavaScript

JavaScript_2th_条件语句和循环语句

2017-04-03 16:52 465 查看

一、条件操作

1）三目运算符

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>三目运算符</title>
<script language="JavaScript">
var result;
result = (3>4)?"Y":"N"
</script>
</head>
<body>
<script language="JavaScript">
document.write(result);//N
</script>
</body>
</html>

2）if-else语句

运行下面程序时的时间是晚上10点，其中Date是JavaScript内置的对象。

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>if-else语句</title>
<script language="JavaScript">
var today = new Date();
var hour = today.getHours();
</script>
</head>
<body>
<script language="JavaScript">
if(hour < 12) {
document.write("Good Morning!");
} else if(hour == 12) {
document.write("Good Noon!");
} else {
document.write("Good Afternoon!");//Good Afternoon!
}
</script>
</body>
</html>

3）switch语句

<!DOCTYPE html>
<html>

<head>
<meta charset="UTF-8">
<title>switch语句</title>
<script language="JavaScript">
var today = new Date();
var hour = today.getHours();
</script>
</head>

<body>
<script language="JavaScript">
switch(hour) {
case 1:
document.write("Good Morning!");
break;
case 2:
document.write("Good Noon!");
break;
case 3:
document.write("Good Afternoon!");
break;
default:
document.write("Hello!");//Hello!
}
</script>
</body>

</html>

二、循环语句

1）while语句

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>while循环</title>
</head>
<body>
<script language="JavaScript">
var i = 1;
while(i < 10) {
document.write(i + " ");//1 2 3 4 5 6 7 8 9
i++;
}
</script>
</body>
</html>

2）do-while循环

<!DOCTYPE html>
<html>

<head>
<meta charset="UTF-8">
<title>do-while循环</title>
</head>

<body>
<script language="JavaScript">
var i = 0;
do {
document.write(i + " ");//0 1 2 3 4 5
i++;
} while (i < 6);
</script>
</body>

</html>

3）for语句

<!DOCTYPE html>
<html>

<head>
<meta charset="UTF-8">
<title>for循环</title>
</head>

<body>
<script language="JavaScript">
var arr = new Array(2, 3, 4, 5);
for(i = 0; i < arr.length; i++) {
document.write(arr[i] + " "); //2 3 4 5
}
</script>
</body>

</html>

三、字符串的charAt()方法

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>charAt()方法</title>
</head>
<body>
<script language="JavaScript">
var str = "Hello World!I am JavaScript.";
var i = 0;
while(i < str.length) {
document.write(str.charAt(i) + " ");//H e l l o W o r l d ! I a m J a v a S c r i p t .
i++;
}
</script>
</body>
</html>

内容来自用户分享和网络整理，不保证内容的准确性，如有侵权内容，可联系管理员处理

标签： JavaScript

相关文章推荐

新的分享

章节导航