> For the complete documentation index, see [llms.txt](https://jen-hsuan-hsieh.gitbook.io/javascript-node-js/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jen-hsuan-hsieh.gitbook.io/javascript-node-js/chapter1/12javascript-quan-gong-lve-ff1a-ke-fu-js-de-qi-guai-bu-fen/127jian-yan-zhi-ming-de-kuang-jia-yu-zi-yuan-ku/1271shen-ru-liao-jie-yuan-shi-ma-ff1a-jqeury-ff08-yi-ff09.md).
# 1.2.7.1.深入瞭解原始碼：jQeury（一）
* 使語法更容易打出來
* 跨瀏覽器
* 操作DOM
```
People
- John Doe
- Jane Doe
- Jim Doe
```
* 選擇器
```
//取得class是people的ul中的li
var q = $("ul.people li")
//印出jQuery.fn.init[3]
console.log(q)
```
* [jQuery 1.12.4 原始碼](https://code.jquery.com/jquery-1.12.4.js)
* jQuery函數不是函數建構子, 所以不用[new](https://jenhsuan.gitbooks.io/javascript-node-js/content/chapter1/125han-shu-jian-gou-zi-3001-300c-new-300d-yu-javascript-de-li-shi/1251han-shu-jian-gou-zi-3001-300c-new-300d-yu-javascript-de-li-shi.html)運算子, 而藉由呼叫函數建構子回傳物件
* 小訣竅: 利用函數呼叫函數建構子, 可以不用使用new運算子
* jQuery.fn是jQuery.prototype的別名
```
jQuery = function( selector, context ) {
// The jQuery object is actually just the init constructor 'enhanced'
// Need init if jQuery is called (just allow error to be thrown if not included)
return new jQuery.fn.init( selector, context );
},
jQuery.fn = jQuery.prototype = {
// The current version of jQuery being used
jquery: version,
constructor: jQuery,
// Start with an empty selector
selector: "",
// The default length of a jQuery object is 0
length: 0,
```