JS练习第三课 - 爱码网

用typeof查看数据类型

<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 src="../js/jquery-3.2.1.min.js"></script>
<script>
    alert("typeof 12345 -->" + typeof 12345 +
    '\ntypeof "abc" -->' + typeof "abc" +
    "\ntypeof document -->" + typeof document);
</script>

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用parseInt解析数字,并求和

<style>
        .d1{
            width: 300px;
            margin: 10px auto;
        }
        input{
            width: 50px;
        }
    </style>
</head>
<body>
<div class="d1">
    <input id="num1" type="text">
    <span> + </span>
    <input id="num2" type="text">
    <span> = </span>
    <span  class="ret"> ? </span>
    <button>求和</button>
</div>
<script src="../js/jquery-3.2.1.min.js"></script>
<script>
    $("button").on("click",function () {
        var num1 = parseInt($("#num1").val());
        var num2 = parseInt($("#num2").val());
        $(".ret").text( num1 + num2);
    })
</script>

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