僅用六種字元來完成Hello World，你能做到嗎？

程式猿DD發表於2020-11-05
字元

Hello World 對於每一個開發者來說都不陌生，因為在我們學習任何一個語言或框架的時候，都會有一個Hello World的案例來幫助我們快速入門。

如果我們使用JavaScript來輸出Hello World的話，可以這樣寫：

alert("Hello World");

放入HTML：

<html>
  <script type="text/javascript">
    alert("Hello World");
  </script>
</html>

在瀏覽器中開啟就可以如下情況輸出Hello World了：

挑戰：僅用六種字元來編寫JavaScripte

上面我們在JavaScript中實現Hello World的時候，除去HTML相關的標籤和屬性，上面的實現語句alert("Hello World");一共使用了13個字元，那麼有沒有辦法用更少的字元來實現一樣的功能呢？今天我們就來挑戰一下：有沒有辦法僅使用6個字元來編寫JavaScripte程式，以實現Hello World的輸出？

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先思考一下，有思路沒？沒思路的話，下面有提示...

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提示：使用這六個字元：(，)，+，[，]，!

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再思考一下，有思路沒？沒思路的話，下面有答案和解析...

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答案：

<html>
<script type="text/javascript">
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</script>
</html>

什麼？你不信這可以輸出Hello World？那麼你可以將其複製下來，放到HTML檔案中，再開啟試試吧！

為什麼？

為什麼我們可以僅使用這6個字元來編寫這些奇奇怪怪的JavaScript程式碼？這完全是由於JavaScript獨特的型別系統和轉換機制。

上面的6個字元可以分為三類：

  • [，]：用於建立陣列
  • !，+：對陣列執行一些操作
  • (，)：對操作進行分組

基礎原理

  • []可以用來建立陣列，而![]則可以返回false
  • 預定義的規則：2 + true，會轉化為2 + 1，最後得到3
  • 預定義的規則：2 + "2"，會轉化為2 + "2"，最後得到"22"

提取字母：![]可以獲取false，![] + []那可以獲取"false"字串，那麼我們就可以通過下標獲取其中的字母，比如：(![] + [])[1]可以獲取false字串中第二位的字母a

提取數字：![]可以獲取false，由於+false可以獲取0，所以+![]就可以獲取到0；由於+true可以獲取1，所以+!![]就可以獲取到1。這樣依靠運算就可以獲取更多其他數字

好了，有了這些基礎基礎知識之後，對於這個神奇的答案知道是怎麼來的了吧？

本文首發：僅用六個字元來完成Hello World，你能做到嗎？，轉載請註明該文章連結

參考資料

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