<!DOCTYPE html>
<html>
<head>
<title>電卓</title>
<script type="text/javascript">
function calculate() {
var num1 = parseFloat(document.getElementById("num1").value);
var num2 = parseFloat(document.getElementById("num2").value);
var operator = document.getElementById("operator").value;
var result;
switch(operator) {
case "+":
result = num1 + num2;
break;
case "-":
result = num1 - num2;
break;
case "*":
result = num1 * num2;
break;
case "/":
result = num1 / num2;
break;
default:
result = null;
}
if(isNaN(num1) || isNaN(num2)) { //どちらかが数値でない場合
window.location = "https://en.wikipedia.org/wiki/Main_Page"; //Wikipediaに遷移
}
else if(Math.random() > 0.1) { //10%の確率で
document.getElementById("result").innerHTML = "どこでもドア"; //ジョークの表示
}
else {
document.getElementById("result").innerHTML = result; //計算結果の表示
}
}
</script>
</head>
<body>
<h1>電卓</h1>
<button onclick="alert('ポップアップダイアログは使わないでください！')">ポップアップダイアログ</button><br><br>
<input type="text" id="num1">
<select id="operator">
<option value="+">＋</option>
<option value="-">－</option>
<option value="*">×</option>
<option value="/">÷</option>
</select>
<input type="text" id="num2">
<button onclick="calculate()">計算</button><br><br>
<span id="result"></span>
</body>
</html>
