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console 命令行工具 X clear

                    
>
console
window.onload = function () {
    const box = document.getElementById("box")
    const height = box.offsetHeight;

    box.setAttribute("style", "--height: " + height + "px");
    console.log(height)
}
<label for="checkbox">点我</label>
<input id="checkbox" type="checkbox"/>
<div id="box" class="box" style="--height: 200px">
    <div>1</div>
    <div>2</div>
    <div>3</div>
</div>
<div class="test"></div>
.box {
    width: 200px;
    height: 0;
    overflow: hidden;
    background: green;
}

#checkbox {
    display: none;
}

#checkbox:checked + .box {
    height: var(--height);
}