从页面顶部获取项目偏移量 [英] Get item offset from the top of page

问题描述

我正在尝试获取div的顶部偏移量，并且我有以下代码在页面滚动时运行：

I am trying to get the top offset of a div, and I have the following code that gets run when the page gets scrolled:

var $elem = document.querySelector(selector);
var elemTop = $elem.offsetTop;
console.log(elemTop);

但滚动时总是打印 0 到控制台，即使元素低于折叠。

But when I scroll it always prints 0 to the console, even though the element is below the fold.

推荐答案

var elmTop = $elem.getBoundingClientRect().top + window.scrollY;

element.getBoundingClientRect（）给出视口内的位置，window.scrollY给出从视口顶部到文档顶部的距离。

element.getBoundingClientRect() gives the position within the viewport, and window.scrollY gives the distance from the top of the viewport to the top of the document.

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