parseint和isNaN用法 

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
</head>

<body>
<script>
    var a='12';
    alert(parseInt(a)+1);//字符串转数字
</script>
</body>
</html>

 

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
</head>

<body>
<input type="text" id="txt1" />
<br/>
<br/>
<input type="text" id="txt2" />
<br/>
<br/>
<input type="button" id="btn" value="点击" />
<script>
    var otxt1=document.getElementById('txt1');
    var otxt2=document.getElementById('txt2');
    var obtn=document.getElementById('btn');
    obtn.onclick=function()
    {
        var n1=parseInt(otxt1.value);
        var n2=parseInt(otxt2.value);
        alert(n1+n2)
    }
</script>
</body>
</html>

 

<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
</head>

<body>
<input type="text" id="txt1" />
<br/>
<br/>
<input type="text" id="txt2" />
<br/>
<br/>
<input type="button" id="btn" value="点击" />
<script>
    var otxt1=document.getElementById('txt1');
    var otxt2=document.getElementById('txt2');
    var obtn=document.getElementById('btn');
    obtn.onclick=function()
    {    
        var n1=parseInt(otxt1.value);
        var n2=parseInt(otxt2.value);
        
        if(isNaN(n1))
            {
                alert('你输入的第一个数字有误！');
            }
        else if(isNaN(n2))
            {
                alert('你输入的第二个数字有误！');
            }
        else
        {
            alert(n1+n2);
        }
    }
</script>
</body>
</html>

 

posted @ 2018-01-20 22:09  绿林豪士  阅读(1213)  评论(0)  编辑  收藏  举报