css后代选择器与子选择器
The descendant selector matches all elements that are descendants of a specified element. The first simple selector within this selector represents the ancestor element—a structurally superior element, such as a parent element, or the parent of a parent element, and so on. The second simple selector represents the descendant element we’re trying to match.
后代选择器匹配作为指定元素的后代的所有元素。 该选择器中的第一个简单选择器代表祖先元素 -结构上较高的元素，例如父元素或父元素的父元素，依此类推。 第二个简单的选择器代表我们要匹配的后代元素。
The combinator we use in a descendant selector is a whitespace character: a space, horizontal tab, carriage return, line feed, or form feed. Since whitespace characters are allowed around all combinators, you can include more than one whitespace character between the simple selectors in a descendant selector.
我们在后代选择器中使用的组合器是一个空白字符：空格，水平制表符，回车，换行或换页。 由于所有组合器周围都允许使用空格字符，因此您可以在子代选择器的简单选择器之间包含多个空格字符。
Consider the following HTML fragment:
考虑以下HTML片段：
<ul> <li>Item 1</li> <li> <ol> <li>Sub-item 2A</li> <li>Sub-item 2B</li> </ol> </li> </ul>We’ll try to match elements in the above fragment using the selector below:
我们将尝试使用以下选择器匹配上述片段中的元素：
ul li { ⋮ declarations }This descendant selector will match all four li elements in the example HTML, because each of those elements has a ul element as its ancestor.
此后代选择器将匹配示例HTML中的所有四个li元素，因为这些元素中的每一个都有一个ul元素作为其祖先。
We can also use descendant selectors to match the li elements within the ol in the example above:
在上面的示例中，我们还可以使用后代选择器来匹配ol中的li元素：
ul * li { ⋮ declarations } ul * * li { ⋮ declarations } ul * ol li { ⋮ declarations } ul li * li { ⋮ declarations } ul ol li { ⋮ declarations } ul li li { ⋮ declarations } ul li ol li { ⋮ declarations }However, there’s no way we can use descendant selectors to match only the list items in the unordered list. To do that, we’d need a child selector.
但是，我们无法使用后代选择器仅匹配无序列表中的列表项。 为此，我们需要一个子选择器。
Take a look at this example of the descendant selector in action:
看一下实际的后代选择器的示例：
ul li { ⋮ declarations }This selector matches all li elements that are descendants of a ul element—that is, every li element that has a ul element as its ancestor.
该选择器匹配作为ul元素后代的所有li元素，即，每个以ul元素为祖先的li元素。
翻译自: https://www.sitepoint.com/descendant-selector-css-selector/
css后代选择器与子选择器
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