圆圈滑动效果

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<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <style>
        .container {
            width: 500px;
            height: 200px;
            border: solid 1px #000000;
            margin: 0 auto;
            position: relative;
        }
        .item {
            width: 100px;
            height: 100px;
            background: red;
            border-radius: 50%;
            position: absolute;
            top: 30px;
            left: 0;
            animation: identifier 2s linear infinite;
        }
        @keyframes identifier {
            50% {
                /* 容器宽度减去自身的宽度 */
                transform: translateX(calc(var(--b) - 100%));
            }
        }
    </style>
    <div class="container">
        <div class="item"></div>
    </div>
    <script>
        const container = document.querySelector(".container");
        function setProperty() {
            const w = container.clientWidth;
            container.style.setProperty("--b", `${w}px`);
        }
        setProperty()
    </script>
</body>

</html>