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選擇器至少可以追溯到“CSS選擇器”。jQuery的源代碼中內嵌了一個叫Sizzle的對象，其實就是選擇器了。在jQuery官網上顯示Sizzle屬于“Other jQuery Foundation Projects”，Sizzle能夠獨立為一個單獨的項目，由此不難體會到選擇器的重要性。看看下面三個頁面，相比之下，jQuery選擇器官方文檔看起來是最“亂”的。
- http://www.w3.org/TR/css3-selectors
- CSS選擇器W3C標準文檔
- https://github.com/jquery/sizzle/wiki/Sizzle-Documentation
- Sizzle文檔
- http://api.jquery.com/category/selectors/
- jQuery選擇器官方文檔
jquery1.9.0源代碼有這樣一行：
- jQuery.find = Sizzle;
- iJs.showObjectNames("window.jQuery.find");
- iJs.showObjectNames("window.Sizzle");
| 語法 | 含義 | 鏈接 | 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 |
選擇器的語法是有標準的，逐一嘗試每一種寫法沒有必要，今天學會了也許明天就忘記，不如有文檔在手，用到時再翻閱。需要想一想的是選擇器的價值所在，從根本上來講，選擇器就是幫助我們避免了遍歷DOM（或者也包括XML?）的麻煩。一個兩個的遍歷代碼其實也不難寫，但是網頁上的互動多了就麻煩了，下面是一個隔行選取的代碼片斷，不難體會其中運用選擇器的奧妙所在：
- <div>
- <b>...測試1...</b>
- <b>...測試2...</b>
- <b>...測試3...</b>
- <b>...測試4...</b>
- </div>
- <script language="javascript">
- var $myObj = jQuery('div b:nth-child(even)');//選擇器
- $myObj.each(
- function(i){
- var tTemp = jQuery(this).text();
- iJs.put(tTemp);//輸出選擇結果
- });
- </script>
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