【测开能力提升-Javascript】JavaScript运算符流程结构

1. 递增递减运算符

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>// 前置递增运算符var age=10++age //类似于age=age+1， 先加1后返回值alert(age)// 后置递增运算符var num=10num++alert(num)// 前置自增和后置自增如果单独使用，效果是一样的// 2. 后置自增口诀：先返回原值，后自加1</script>
</head>
<body></body>
</html>

2 逻辑中断

2.1 逻辑与

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>// 如果表达式1 结果为真，则返回表达式2  如果表达式1 结果为假，则返回表达式1alert(0 && 123)alert(123 && 456)</script>
</head>
<body></body>
</html>

在这里插入图片描述

2.2 逻辑或

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>// 如果表达式1 结果为真，则返回表达式1   如果表达式1 结果为假，则返回表达式2alert(0||111)alert(123||456)</script>
</head>
<body></body>
</html>

在这里插入图片描述

3. if条件判断

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>if (0) {alert("hello world")} else {alert("error")}</script>
</head>
<body></body>
</html>

4. switch分支语句

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>switch (2) {case 1:alert("1")breakcase 2:alert("2")breakcase 3:alert("3")breakdefault:alert("没有匹配结果")}</script>
</head>
<body></body>
</html>

5. for循环

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>for (var i=1; i<=100; i++){alert("hello world")}</script>
</head>
<body></body>
</html>

6. while循环

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title><script>var num = 1while (num<=100) {alert('Hello World')}</script>
</head>
<body></body>
</html>