黑马程序员-JavaScript-day02
01-赋值运算符
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = 1
num += 2
num += 3
document.write(num)
</script>
</body>
</html>
02-自增运算符
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = 1
num++
++num
document.write(num)
</script>
</body>
</html>
03-比较运算符
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
console.log(3 > 5)
console.log(3 >= 3)
console.log(2 == 2)
console.log(2 == '2')
console.log(2 === '2')
console.log(NaN === NaN)
console.log(2 !== '2')
console.log(2 != '2')
console.log('a' < 'b')
console.log('aa' < 'ab')
console.log('abc' < 'ab');
</script>
</body>
</html>
04-逻辑运算符
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = +prompt('请输入一个数')
document.write((num % 4 === 0) && (num % 100 !== 0))
console.log('---------------------')
console.log('逻辑与')
console.log(false && true)
console.log(3 < 5 && 3 > 2)
console.log(3 < 5 && 3 < 2)
console.log('逻辑或')
console.log(true || true)
console.log(false || true)
console.log(false || false)
console.log('逻辑非')
console.log(!true)
console.log(!false)
console.log('---------------------')
let num1 = 6
console.log(num1 > 5 && num1 < 10)
</script>
</body>
</html>
05-if单分支语句
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
if (2 === '2') {
console.log('执行语句1')
}
if (0) {
console.log('执行语句2')
}
if ('111') {
console.log('执行语句3')
}
if ('') {
console.log('执行语句4')
}
</script>
</body>
</html>
06-双分支语句
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let name = prompt('请输入用户名')
let pad = prompt('请输入密码')
if (name === '123' && pad === '123') {
alert('用户名和密码均正确')
} else {
alert('密码或用户名不正确')
}
</script>
</body>
</html>
07-闰年案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = +prompt('请输入年份:')
if (num % 4 === 0 && num % 100 !== 0 || num % 400 == 0) {
alert('今年是闰年')
} else {
alert('不是闰年')
}
</script>
</body>
</html>
08-if多分支语句
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let score = +prompt('请输入成绩')
if (score >= 90) {
alert('真优秀')
} else if (score >= 70) {
alert('良好')
} else if (score >= 60) {
alert('及格')
} else {
alert('不及格')
}
</script>
</body>
</html>
09-三元运算符
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num1 = prompt('请输入第一个数')
let num2 = prompt('请输入第二个数')
alert(num1 > num2 ? num1 : num2)
</script>
</body>
</html>
10-数字补0案例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = prompt('请输入一个数字')
alert(num < 10 ? 0 + num : num)
</script>
</body>
</html>
11-switch分支语句
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = +prompt('请输入一个数字')
switch (num) {
case 1:
alert('你选择的是语句1')
break
case 2:
alert('你选择的是语句2')
break
case 3:
alert('你选择的是语句3')
break
default:
alert('没有匹配的选项')
}
</script>
</body>
</html>
12-简单计算器
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num1 = +prompt('请输入第一个数字')
let num2 = +prompt('请输入第二个数字')
let temp = prompt('请输入运算符:')
switch (temp) {
case '+':
alert(num1 + num2)
break
case '-':
alert(num1 - num2)
break
case '*':
alert(num1 * num2)
break
case '/':
alert(num1 / num2)
break
default:
alert('请输入合法运算!')
}
</script>
</body>
</html>
13-断点调试
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let num = 1
num = num + 1
alert(num)
</script>
</body>
</html>
14-while循环
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let end = +prompt('要打印几次?')
let i = 1
let sum = 0
let sum1 = 0
while (i <= end) {
document.write(i)
document.write('我很好')
sum += i
if (i % 2 === 0) {
sum1 += i
}
i++
}
document.write(`1-100的和是${sum}`)
document.write(`1-100的偶数和是${sum1}`)
</script>
</body>
</html>
15-退出循环-1
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let i = 0
while (i < 5) {
if (i === 3) {
break
}
alert(`第${i}次打印`)
i++
}
alert('循环结束')
</script>
</body>
</html>
15-退出循环-2
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let i = 0
while (i < 5) {
if (i === 3) {
i++
continue
}
alert(`这是第${i}个`)
i++
}
</script>
</body>
</html>
16-你爱我吗
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
while (true) {
let src = prompt('你爱我吗')
if (src === '爱') {
break
}
}
</script>
</body>
</html>
17-综合案例-加减乘除
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
while (true) {
let src = prompt('请输入运算符')
if (src === 'q') {
break
}
let num1 = +prompt('第一个数字')
let num2 = +prompt('第二个数字')
switch (src) {
case '+':
alert(num1 + num2)
break
case '-':
alert(num1 - num2)
break
case '*':
alert(num1 * num2)
break
case '/':
alert(num1 / num2)
break
default:
alert('请重新输入')
break
}
}
</script>
</body>
</html>
17-综合案例-简易ATM
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<script>
let sum = 0
let temp = 1
while (temp) {
let num = +prompt(`请输入您的选择:
1.存钱
2.取钱
3.查看余额
4.退出
`)
// 可以直接在switch外面判断num=4的情况
switch (num) {
case 1:
let money1 = +prompt('您要存多少钱')
sum += money1
break
case 2:
let money2 = +prompt('您要取多少钱')
if (money2 > sum) {
alert('您没有这么多钱,请重新选择')
break
}
sum -= money2
break
case 3:
alert(`您的余额是${sum}元`)
break
case 4:
temp = 0
break
default:
alert('请重新选择')
break
}
}
</script>
</body>
</html>
原文地址:https://blog.csdn.net/qyk666/article/details/142414234
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