以下是老師叫我做的作業，
1、用戶輸入一個年份，用來判斷是閏年還是平年
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<h2>判斷是平年還是閏年</h2>
原數據:<input id="old" type="text">
操作:<input type = "button" value="判斷" οnclick="cal()">
新數據:<input id="new" type="text">
<script>
function cal()
{
var a = document.getElementById("old").value;
if((a%4==0)&&(a%100!=0)||(a%400==0))
document.getElementById("new").value = "閏年";
else
document.getElementById("new").value = "平年";
}
</script>
</body>
</html>
嗯哼，就這樣，
2、去除字符串的前後的空格
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<h2>去除字符串前後的空格</h2>
原數據:<input id="old" type="text">
操作:<input type = "button" value="操作" οnclick="cal()">
新數據:<input id="new" type="text">
<script>
function cal()
{
var a = document.getElementById("old").value;
var start, end;
for(var i = 0;i < a.length; i++)
{
if(a[i] == " ")
{
continue;
}else{
start = i;
break;
}
}
for(var i = start; i < a.length; i++)
{
if(a[i] == "")
{
end = i - 1;
break;
}
end = i;
}
document.getElementById("new").value = a.substring(start,end)
}
</script>
</body>
</html>
如下圖所示：
