练习1:统计包含“a”或“A”的字符串的个数
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title>统计包含“a”或“A”的字符串的个数</title>
</head>
<body>
<script type="text/javascript">
var countryList=["America","Greece","Britain","Canada","China","Egypt"];
var count=0;
document.write("在以下字符中:<br/>");
for(var i=0;i<countryList.length;i++){
document.write(countryList[i]+"<br />");
if(countryList[i].indexOf("a")!=-1||countryList[i].indexOf("A")!=-1)
count++;
}
document.write("共有"+count+"个字符串中包含a或A。");
</script>
</body>
</html>
练习2:计算圆的周长和面积
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>计算圆的周长和面积</title>
</head>
<body>
<div>
<p>圆的半径:<input id="r" type="text"></p>
<p>圆的周长:<input id="cir" type="text"></p>
<p>圆的面积:<input id="area" type="text"></p>
</div>
<script>
var r = prompt('请输入圆的半径');
r = parseFloat(r) && Number(r); // 获取输入的纯数字,其余情况皆转为NaN
if(!isNaN(r)){
var cir = 2*Math.PI*r;
var area = Math.PI*r*r;
document.getElementById('r').value=r;
document.getElementById('cir').value=cir.toFixed(2);
document.getElementById('area').value=area.toFixed(2);
}
</script>
</body>
</html>
练习3:用if语句判断某学生成绩是否及格
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>用if语句判断成绩是否及格</title>
</head>
<body>
<script>
var score = prompt('请输入一个成绩');
if(score>=60)
alert("及格!");
else
alert("不及格!");
</script>
</body>
</html>
练习4:switch语句判断任意年份是十二生肖中的哪一年
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>switch语句判断任意年份是十二生肖中的哪一年</title>
</head>
<body>
<script>
var year = prompt("请输入1900到2022年之间的任一年份");
var x = (year-1900)%12;
switch(x){
case 0: alert(year+"年是鼠年!"); break;
case 1: alert(year+"年是牛年!"); break;
case 2: alert(year+"年是虎年!"); break;
case 3: alert(year+"年是兔年!"); break;
case 4: alert(year+"年是龙年!"); break;
case 5: alert(year+"年是蛇年!"); break;
case 6: alert(year+"年是马年!"); break;
case 7: alert(year+"年是羊年!"); break;
case 8: alert(year+"年是猴年!"); break;
case 9: alert(year+"年是鸡年!"); break;
case 10: alert(year+"年是狗年!"); break;
case 11: alert(year+"年是猪年!"); break;
}
</script>
</body>
</html>
练习5:九九乘法表
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>九九乘法表</title>
<style>
table{border-collapse:collapse;}
table td{border:1px solid #ccc;padding:3px 6px;}
</style>
</head>
<body>
<div id="table"></div>
<script>
var str = '<table>';
for(var i=1;i<=9;++i){
str+='<tr>';
for(var j=1;j<=i;++j){
str += '<td>' + j + 'x' + i + '=' + (j*i) + '</td>';
}
str+='</tr>';
}
str += '</table>';
// 将拼接后的字符串显示到页面中
document.getElementById('table').innerHTML = str;
</script>
</body>
</html>
WEB安全总结: indexOf()方法经常会遇到!!! (1)indexOf() 方法
(2)lastIndexOf() 方法
(2)修改文本域的值的方法:document.getElementById(‘r’).value=r; (3)prompt提示框格式:prompt”提示信息”,”输入框的默认信息”); (4)alert弹窗警告格式:alert(“提示信息”); (5)console.log控制台输出信息:console.log(“代输出的信息”); 2021.09.17 (课上)
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