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>
在瀏覽器中打開就可以如下情況輸出Hello World了：
挑戰：僅用六種字符來編寫JavaScripte
上面我們在JavaScript中實現Hello World的時候，除去HTML相關的標簽和屬性，上面的實現語句alert("Hello World");一共使用了13個字符，那么有沒有辦法用更少的字符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個字符來編寫JavaScripte程序，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：使用這六個字符：(，)，+，[，]，!
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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>
什么？你不信這可以輸出Hello World？那么你可以將其復制下來，放到HTML文件中，再打開試試吧！
為什么？
為什么我們可以僅使用這6個字符來編寫這些奇奇怪怪的JavaScript代碼？這完全是由於JavaScript獨特的類型系統和轉換機制。
上面的6個字符可以分為三類：
[，]：用於創建數組!，+：對數組執行一些操作(，)：對操作進行分組
基礎原理
[]可以用來創建數組，而![]則可以返回false- 預定義的規則：
2 + true，會轉化為2 + 1，最后得到3 - 預定義的規則：
2 + "2"，會轉化為2 + "2"，最后得到"22"
提取字母：![]可以獲取false，![] + []那可以獲取"false"字符串，那么我們就可以通過下標獲取其中的字母，比如：(![] + [])[1]可以獲取false字符串中第二位的字母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后，對於這個神奇的答案知道是怎么來的了吧？
本文首發：僅用六個字符來完成Hello World，你能做到嗎？，轉載請注明該文章鏈接
參考資料
歡迎關注我的公眾號：程序猿DD，獲得獨家整理的免費學習資源助力你的Java學習之路！另每周贈書不停哦～