<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>计算器</title>
<script type="text/javascript">
window.onload = function() {
var otxt1 = document.getElementById('txt1');
var otxt2 = document.getElementById('txt2');
var obtn = document.getElementById('btn');
obtn.onclick = function() {
var sum = parseInt(otxt1.value) + parseInt(otxt2.value);
if(isNaN(sum)) {
alert('您输入的有误');
} else {
alert(sum);
}
}
}
</script>
</head>
<body>
<input type="text" id="txt1" value="" />
<label>+</label>
<input type="text" id="txt2" value="" />
<input type="button" name="" id="btn" value="计算" />
</body>
</html>
