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用typeof查看数据类型&&用parseInt解析数字，并求和

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<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>用typeof查看数据类型</title>
<style>
pre{color:green;padding:10px 15px;background:#f0f0f0;border:1px dotted #333;font:12px/1.5 Courier New;}
span{color:#999;}
</style>
</head>
<body>
<pre>
&lt;script type="text/javascript"&gt;
    alert(typeof 12345);    <span>//输出number</span>
    alert(typeof "abc");    <span>//输出string</span>
    alert(typeof document);    <span>//输出object</span>
&lt;/script&gt;
</pre>
<script>
alert("typeof 12345 → " + typeof 12345 + "
      

typeof "abc" → " + typeof "abc" + "
      

typeof document → " + typeof document
      );
</script>
</body>
</html>

用parseInt解析数字，并求和

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>用parseInt解析数字，并求和</title>
<style>
body{font:12px/1.5 arial;text-align:center;}
.f-text{50px;border:1px solid #ccc;background:#f0f0f0;font-family:inherit;padding:3px;}
span{color:green;padding-right:10px;font-weight:700;}
strong{padding:0 10px;}
</style>
<script type="text/javascript">
window.onload = function ()
{
    var aInput = document.getElementsByTagName("input");
    var aSpan = document.getElementsByTagName("span")[0];
    var i = 0;
    
    for (i = 0; i < aInput.length - 1; i++)
    {
        aInput[i].onkeyup = function ()
        {
            this.value = this.value.replace(/[^d]/,"")
        }    
    }
    
    aInput[2].onclick = function ()
    {
        (aInput[0].value == "" || aInput[1].value == "") ?
        alert("请输入数字！") :
        aSpan.innerHTML = parseInt(aInput[0].value) + parseInt(aInput[1].value);
    }
};
</script>
</head>
<body>
<input type="text" class="f-text" /><strong>+</strong><input type="text" class="f-text" /><strong>=</strong><span>?</span><input type="button" value="求和" />
</body>
</html>

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原文地址：https://www.cnblogs.com/mayufo/p/4474971.html