Selection.focusOffset
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2017.
只读属性 Selection.focusOffset 返回选区终点（鼠标松开瞬间所记录的那个点）在焦点（Selection.focusNode）中的偏移量。返回值从零开始计数，如果选区（Selection）在焦点（Selection.focusNode）的第一个字符前结束，返回值为 0。
语法
offset = sel.focusOffset
规范
| Specification |
|---|
| Selection API # dom-selection-focusoffset |
浏览器兼容性
BCD tables only load in the browser
相关链接
Selection, 这个属性所属的接口。