console 命令行工具 X clear

console

window.onscroll = scroll;

function scroll()
{
    let height = 3000 - document.querySelector('html').clientHeight;
    let temp;
    if (window.pageYOffset < height/3) temp = 1;
    else if (window.pageYOffset < height/3*2) temp = 2;
    else if (window.pageYOffset < height/3*3) temp = 3;
    console.log(temp);
    
}

<body>
    <div id="id1">
        <div class="class1 yellow">xxxx</div>
        <div class="class1 green">123</div>
    </div>
</body>

html {
    height: 100vh;
    width: 100vw;
}

body {
    height: 3000px;
    width: 100vw;
    background: red;
    /* min-height: 2000px; */
    min-width: 500px;
    margin: 0;
    /* overflow: hidden; */
}

#id1 {
    position: fixed;
    height: 100vh;
    background: blue;
    width: 100vw;
}

.class1 {
    width: 100%;
    height: 50%;
}

.yellow {
    background: yellow;
}

.green {
    background: green;
}