# 1.2.6.3.嚴謹模式

* 嚴謹模式
  * 可以避免某些情況下的錯誤

    ```
    //打錯字
    var Person;

    persom = {};
    //印出Object{}
    console.log(persom);
    ```
  * use strict一定要在檔案或是函數的最上方
  * 一定要宣告

    ```
    "use strict"
    //打錯字
    var Person;

    persom = {};
    //印出Uncaught ReferenceError: persom is not defined
    console.log(persom);
    ```
* [參考資料: MDN](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode)


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