> 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/121zhi-xing-huan-jing-yu-ci-hui-huan-jing/1211quan-yu-huan-jing-yu-quan-yu-wu-jian.md).

# 1.2.1.1.全域環境與全域物件

* 全域執行環境 (global Execution context)被執行與建立
* 全域環境: Not inside the function
* JavaScript engine會建立兩個東西, 在全域環境下下列兩者相同, 不須程式碼就能創造
  * Global Object (window)
    * 不同tab有不同Execution context, 會產生不同window
  * this
    * 參照到window
  * 其他
    * Outer environment
      * null
    * Code
* 如果在全域環境定義變數或函式, 則變數或函式可在this中找到