版本：
文件：
- https://cdn.bootcdn.net/ajax/libs/jquery-visible/1.2.0/jquery.visible.js
- https://cdn.bootcdn.net/ajax/libs/jquery-visible/1.2.0/jquery.visible.min.js
Quickly check if an element is within the browsers visible viewport, regardless of scroll position. If a user can see this element, the function will return true.