练习题，请老师检查
来源：2-1 什么是表达式和运算符
慕莱坞855634
2021-01-06 15:35:20
<!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>
// 三角形面积
var a = Number(prompt('请输入三角形的底边长'));
var b = Number(prompt('请输入三角形的高'));
var s = 0.5 * a * b;
alert('三角形的面积是' + s);
</script>
<script>
// 算术运算
var a = 4;
var b = 5;
console.log(a + b);
console.log(a - b);
console.log(a * b);
console.log(a / b);
console.log(a % b);
</script>
<script>
// 数据类型之NaN
var a = null;
var b = 10;
var c = "我是字符串";
var d = "10";
var e = undefined;
console.log(isNaN(a));
console.log(isNaN(b));
console.log(isNaN(c));
console.log(isNaN(d));
console.log(isNaN(e));
</script>
<script>
// 逻辑操作符
var x=0,y=undefined;
var m=1,n="imooc";
console.log(x && y);
console.log(m && n);
</script>
<script>
// 逻辑操作符
var x=NaN,y=undefined,z=1;
var m=1,n="0",j=33;
var a=!(!undefined),b=!0;
console.log(x||y||z);
console.log(m||n||j);
console.log(a||b);
</script>
<script>
// 赋值运算
var a=5;
var b=7;
var c = a;
a = b;
b = c;
document.write('a = ' + a + '; b = ' + b);
</script>
<script>
// ++和--的运算
var a = 4, b = 5;
var result = (a++) + (--b);
console.log(result);
var result = (a++) - (--b);
console.log(result);
var result = (a++) * (--b);
console.log(result);
var result = (a++) / (--b);
console.log(result);
</script>
<script>
// 闰年判断
var year = Number(prompt('请输入你的出生年份'));
alert((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
</script>
</body>
</html>
1回答
-
好帮手慕久久
2021-01-06
同学你好，代码正确，很棒，祝学习愉快！
0
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