根据输入的半径值，用ＪＳ代码实现点击“计算”按钮时，计算并显示周长和面积。

最新推荐文章于 2023-07-04 00:03:39 发布

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最新推荐文章于 2023-07-04 00:03:39 发布

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分类专栏：笔记

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!DOCTYPE html>
<html lang="zh-CN">
<head>
    <meta charset="UTF-8">
    <title>计算圆</title>
</head>
<body>
<div class="box1">
    <label for="radius">圆的半径:</label>
    <input type="text" id="radius">
</div>
<div class="box2">
    <label for="perimeter">圆的周长:</label>
    <input type="text" id="perimeter">
</div>
<div class="box3">
    <label for="area">圆的面积:</label>
    <input type="text" id="area">
</div>
<script>
    let radius = document.getElementById('radius'),
        perimeter = document.getElementById('perimeter'),
        area = document.getElementById('area');

    radius.oninput = function () {
        let r = radius.value;
        let res_perimeter = Math.PI * 2 * r;
        let res_area = Math.PI * Math.pow(r, 2);
        if (r === '0') {
            perimeter.value = '0';
            area.value = '0';
        } else {
            perimeter.value = res_perimeter.toString().substr(0, 4).concat('0');
            area.value = res_area.toString().substr(0, 4).concat('0');
        }
    };

</script>
</body>
</html>