<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>求和</title>
<script>
window.onload=function(){
var oTxt1=document.getElementById('txt1');
var oTxt2=document.getElementById('txt2');
var oBtn=document.getElementById('btn1');
oBtn.onclick=function(){
alert(parseInt(oTxt1.value)+parseInt(oTxt2.value));
}
}
</script>
</head>
<body>
<input id="txt1" type="text"/>
<input id="txt2" type="text"/>
<input id="btn1" type="button" value="求和">
</body>
</html>
NaN:not a number不是数字
12+NaN=NaN
NaN!=NaN
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>NaN</title>
</head>
<script>
var a=parseInt('abc');
var b=parseInt('def');
alert(a==b);
</script>
<body>
</body>
</html>
判断是否是NaN
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>nan</title>
<script>
var a=parseInt('abc');
alert(isNaN(a));
</script>
</head>
<body>
</body>
</html>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>求和</title>
<script>
window.onload=function() {
var oTxt1 = document.getElementById('txt1');
var oTxt2 = document.getElementById('txt2');
var oBtn= document.getElementById('btn1');
oBtn.onclick=function(){
var n1=parseInt(oTxt1.value);
var n2=parseInt(oTxt2.value);
if(isNaN(n1)){
alert('您输入的第一个数字有误');}
else if(isNaN(n2)){
alert('您输入的第二个数字有误');
}
else{
alert(n1+n2);
}
}
}
</script>
</head>
<body>
<input id="txt1" type="text"/>
<input id="txt2" type="text"/>
<input id="btn1" type="button" value="求和">
</body>
</html>
FLOAT
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var a='3.5';
//alert(parseInt(a));
alert(parseFloat(a));
</script>
</body>
</html>
