点击后加1或减去1

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>点击后加1或减去1</title>
</head>
<body>
    <span id="num">0</span>
<button onclick="document.getElementById('num').innerHTML++">点击加1</button>


    <span id="num1">55</span>
    <button onclick="document.getElementById('num1').innerHTML--">点击减1</button>
</body>
</html>

效果图：

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原文地址：https://www.cnblogs.com/heyiming/p/7007943.html