javascript 滚动顶部

Posted 2021-05-03

function getCoords(elem) { // crossbrowser version
    var box = elem.getBoundingClientRect();

    var body = document.body;
    var docEl = document.documentElement;

    var scrollTop = window.pageYOffset || docEl.scrollTop || body.scrollTop; // 获得整个页面已经滚动的距离
    var scrollLeft = window.pageXOffset || docEl.scrollLeft || body.scrollLeft;

    var clientTop = docEl.clientTop || body.clientTop || 0;
    var clientLeft = docEl.clientLeft || body.clientLeft || 0;

    var top  = box.top +  scrollTop - clientTop; // 整个页面已经滚动的距离-(目标元素与视口的距离) = 目标元素相对body上边界的距离
    var left = box.left + scrollLeft - clientLeft;

    return { top: Math.round(top), left: Math.round(left) };
}