可以jQuery告诉是否< select>的< option>元素当前显示？ [英] Can jQuery tell if the <option>s of a <select> element are currently displayed?

问题描述

可能重复：

我的客户希望我显示一些简单的说明一旦用户以使得< option> 列表的方式与我们的< select> 元素交互我想，如果在< select> 框下面没有太多空间，一些浏览器向上打开，则下拉（或下拉然后，一旦用户做出新的选择并因此导致选项列表消失，或者如果他们简单地关闭选项列表而不进行改变，则指令将再次消失。

My customer would like me to display some simple instructions once the user interacts with our <select> element in such a way as to cause the <option> list to drop down (or "drop up", I suppose, since some browsers open upwards if there is not much room beneath the <select> box). And then the instructions should disappear again once the user has either made a new selection and thus caused the option list to disappear, or if they simply close the option list without making a change.

我以为我在使用CSS / CSS3选择器和jQuery事件使得类似< div> 的指令出现和消失时有相当丰富的经验，但是对于这种情况，我无法确定是否有一种方法来告诉< select> 框不仅仅是活动或专注当选择框仍然关闭并且不显示其选项列表 - 但实际上是打开时，可以是真的。没有我已经测试的CSS伪选择器或jQuery事件让我看到，更少响应，< select> 的开放状态或闭合状态， code>框。

I thought that I was fairly well-experienced with using both CSS/CSS3 selectors and jQuery events to make things like a <div> full of instructions appear and disappear, but for this case I am having trouble figuring out whether there is a way to tell when a <select> box is not merely "active" or "focused" — both of which can be true while the select box is still closed and not displaying its list of options — but actually open. None of the CSS pseudo-selectors or jQuery events that I have tested let me "see", much less respond to, the state of the open-ness or closed-ness of the <select> box.

有没有人知道如何设置触发器或写一个CSS规则，取决于当前是否显示选项列表？

Does anyone know how I can set a trigger or write a CSS rule that depends on whether the options list is currently displayed?

推荐答案

如果 $（'myID：focus'） ，还有另一种方法。

If $('myID:focus') is not sufficient, I doubt, that there is another way.

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