选择器至少可以追溯到“CSS选择器”。jQuery的源代码中内嵌了一个叫Sizzle的对象，其实就是选择器了。在jQuery官网上显示Sizzle属于“Other jQuery Foundation Projects”，Sizzle能够独立为一个单独的项目，由此不难体会到选择器的重要性。看看下面三个页面，相比之下，jQuery选择器官方文档看起来是最“乱”的。
http://www.w3.org/TR/css3-selectorsCSS选择器W3C标准文档 https://github.com/jquery/sizzle/wiki/Sizzle-DocumentationSizzle文档 http://api.jquery.com/category/selectors/jQuery选择器官方文档
jquery1.9.0源代码有这样一行：
jQuery.find = Sizzle;
导入jquery.js和sizzle.js，可以看到jQuery.find和Sizzle确实是一回事。
iJs.showObjectNames("window.jQuery.find"); iJs.showObjectNames("window.Sizzle");
[Object] window.jQuery.find
|--[function] attr
|--[function] compile
|--[function] contains
|--[function] error
|--[function] getText
|--[function] isXML
|--[function] matches
|--[function] matchesSelector
|--[function] setDocument
|--[function] uniqueSort
|--[object] selectors
[Object] window.Sizzle
|--[function] attr
|--[function] compile
|--[function] contains
|--[function] error
|--[function] getText
|--[function] isXML
|--[function] matches
|--[function] matchesSelector
|--[function] setDocument
|--[function] uniqueSort
|--[object] selectors 既然Sizzle自称"supports virtually all CSS 3 Selectors"，那么不妨就参考下面W3C描述吧，再难找到更好的文档片断了（点击链接可查看语法细节），不是么？ (备注：这个Table贴过来总是出现显示问题，于是对html代码进行了编辑，其中一个替换是(<a\shref="[^">]*">)[^<]*(</a>)替换为$1更多$2)
| 语法 | 含义 | 链接 | 版本 |
|---|---|---|---|
| * | any element | 更多 | 2 |
| E | an element of type E | 更多 | 1 |
| E[foo] | an E element with a "foo" attribute | 更多 | 2 |
| E[foo="bar"] | an E element whose "foo" attribute value is exactly equal to "bar" | 更多 | 2 |
| E[foo~="bar"] | an E element whose "foo" attribute value is a list of whitespace-separated values, one of which is exactly equal to "bar" | 更多 | 2 |
| E[foo^="bar"] | an E element whose "foo" attribute value begins exactly with the string "bar" | 更多 | 3 |
| E[foo$="bar"] | an E element whose "foo" attribute value ends exactly with the string "bar" | 更多 | 3 |
| E[foo*="bar"] | an E element whose "foo" attribute value contains the substring "bar" | 更多 | 3 |
| E[foo|="en"] | an E element whose "foo" attribute has a hyphen-separated list of values beginning (from the left) with "en" | 更多 | 2 |
| E:root | an E element, root of the document | 更多 | 3 |
| E:nth-child(n) | an E element, the n-th child of its parent | 更多 | 3 |
| E:nth-last-child(n) | an E element, the n-th child of its parent, counting from the last one | 更多 | 3 |
| E:nth-of-type(n) | an E element, the n-th sibling of its type | 更多 | 3 |
| E:nth-last-of-type(n) | an E element, the n-th sibling of its type, counting from the last one | 更多 | 3 |
| E:first-child | an E element, first child of its parent | 更多 | 2 |
| E:last-child | an E element, last child of its parent | 更多 | 3 |
| E:first-of-type | an E element, first sibling of its type | 更多 | 3 |
| E:last-of-type | an E element, last sibling of its type | 更多 | 3 |
| E:only-child | an E element, only child of its parent | 更多 | 3 |
| E:only-of-type | an E element, only sibling of its type | 更多 | 3 |
| E:empty | an E element that has no children (including text nodes) | 更多 | 3 |
| E:link E:visited | an E element being the source anchor of a hyperlink of which the target is not yet visited (:link) or already visited (:visited) | 更多 | 1 |
| E:active E:hover E:focus | an E element during certain user actions | 更多 | 1 and 2 |
| E:target | an E element being the target of the referring URI | 更多 | 3 |
| E:lang(fr) | an element of type E in language "fr" (the document language specifies how language is determined) | 更多 | 2 |
| E:enabled E:disabled | a user interface element E which is enabled or disabled | 更多 | 3 |
| E:checked | a user interface element E which is checked (for instance a radio-button or checkbox) | 更多 | 3 |
| E::first-line | the first formatted line of an E element | 更多 | 1 |
| E::first-letter | the first formatted letter of an E element | 更多 | 1 |
| E::before | generated content before an E element | 更多 | 2 |
| E::after | generated content after an E element | 更多 | 2 |
| E.warning | an E element whose class is "warning" (the document language specifies how class is determined). | 更多 | 1 |
| E#myid | an E element with ID equal to "myid". | 更多 | 1 |
| E:not(s) | an E element that does not match simple selector s | 更多 | 3 |
| E F | an F element descendant of an E element | 更多 | 1 |
| E > F | an F element child of an E element | 更多 | 2 |
| E + F | an F element immediately preceded by an E element | 更多 | 2 |
| E ~ F | an F element preceded by an E element | 更多 | 3 |
需注意，jQuery()和jQuery.find()返回的对象类型是不一样的，前者是jQuery.fn，后者是Sizzle。例如，jQuery('html body div#dbg');和jQuery.find('html body div#dbg');都是“选择”了id为dbg的div，但是前者表示为jQuery.fn对象，后者表示为Sizzle对象。
选择器的语法是有标准的，逐一尝试每一种写法没有必要，今天学会了也许明天就忘记，不如有文档在手，用到时再翻阅。需要想一想的是选择器的价值所在，从根本上来讲，选择器就是帮助我们避免了遍历DOM（或者也包括XML?）的麻烦。一个两个的遍历代码其实也不难写，但是网页上的互动多了就麻烦了，下面是一个隔行选取的代码片断，不难体会其中运用选择器的奥妙所在：
<div> <b>...测试1...</b> <b>...测试2...</b> <b>...测试3...</b> <b>...测试4...</b> </div> <script language="javascript"> var $myObj = jQuery('div b:nth-child(even)');//选择器 $myObj.each( function(i){ var tTemp = jQuery(this).text(); iJs.put(tTemp);//输出选择结果 }); </script>调试信息:
...测试2...
...测试4...
共同学习，写下你的评论
评论加载中...
作者其他优质文章
