区别：checked和：在jQuery中使用选项元素时选择 [英] Difference between :checked and :selected when working with option elements in jQuery

问题描述

：选中和：选中似乎在使用<时提供相同的结果;选项> 元素。使用一个优于另一个是否有任何优势？如果：selected 与：check 做同样的事情，那么将它包含在jQuery中的原因是什么？

Both :checked and :selected seem to provide equal results when working with <option> elements. Is there any advantage to using one over the other? If :selected does the same thing as :checked, what is the reason for it to be included in jQuery at all?

示例：

<p class="p1">Select a value</p>
<p class="p2">Select a value</p>

<select>
    <option value="a">Option one</option>
    <option value="b">Option two</option>
</select>


$('select').on('change', function(){

    $('.p1').text(function() { 
        return $('option:selected').text();
    });

    $('.p2').text(function() { 
        return $('option:checked').text();
    });
});

JS Bin演示

推荐答案

判断文档，似乎：selected 与：已检查，但它仅匹配选项元素。这是由HTMLOptionElement证实的，它是DOM中唯一具有选择的属性的元素类型（这是：selected 用于测试元素的选择性）。换句话说，当您只对选项元素感兴趣时，两个选择器都是相同的 - 除了：selected 是非-standard。

Judging by the documentation, it seems that :selected is identical to :checked with the exception that it only matches option elements. This is corroborated by HTMLOptionElement being the only element type in the DOM to have a selected property (which is what :selected uses to test the selectedness of an element). In other words, when you're only interested in option elements, both selectors are identical — except :selected is non-standard.

由于文档本身建议使用标准选择器来最大化性能（并且因为为什么不使用标准选择器而不是非 - 如果有选择的标准吗？），我认为没有任何理由在任何情况下都使用：selected 。我想不出任何情况 *：选择比选项更好：选中（严重的是，当是你最后一次使用这种没有类型选择器的伪类吗？）。

Since the documentation itself recommends using standard selectors to maximize performance (and because why would you not use a standard selector over a non-standard one if given the choice?), I don't think there is any reason to use :selected in any situation ever. I can't think of any situation in which *:selected would be preferable to option:checked (seriously, when was the last time you used a pseudo-class of this kind without a type selector?).

也许它被包含在jQuery中的原因是因为选择器3（其中） ：已检查出现）jQuery诞生时尚未标准化，但：已检查已在规范中自2000年以来，所以我并不完全相信这是真的原因。

Perhaps the reason it was included in jQuery was because Selectors 3 (in which :checked appears) wasn't yet standardized at the time jQuery was born, but :checked has been in the spec since 2000, so I'm not entirely convinced that's really the reason.

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