Hello World 对于每一个开发者来说都不陌生，因为在我们学习任何一个语言或框架的时候，都会有一个Hello World的案例来帮助我们快速入门。
如果我们使用JavaScript来输出Hello World的话，可以这样写：
alert("Hello World");
放入html：
<html>
<script type="text/JavaScript">
alert("Hello World");
</script>
</html>
在浏览器中打开就可以如下情况输出Hello World了
挑战：仅用六个字符来编写JavaScripte
上面我们在JavaScript中实现Hello World的时候，除去HTML相关的标签和属性，上面的实现语句 alert("Hello World"); 一共使用了13个字符，那么有没有办法用更少的字符来实现一样的功能呢？今天我们就来挑战一下： 有没有办法仅使用6个字符来编写JavaScripte程序，以实现Hello World的输出？
先思考一下，有思路没？没思路的话，下面有提示…
提示：使用这六个字符： ( ， ) ， + ， [ ， ] ， !
再思考一下，有思路没？没思路的话，下面有答案和解析…
答案：
<html>
<script type="text/javascript">
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</script>
</html>
什么？你不信这可以输出Hello World？那么你可以将其复制下来，放到HTML文件中，再打开试试吧！
https://www.houdianzi.com/dglogo/ 东莞logo设计
为什么？
为什么我们可以仅使用这6个字符来编写这些奇奇怪怪的JavaScript代码？这完全是由于JavaScript独特的类型系统和转换机制。
上面的6个字符可以分为三类：
- [ ， ] ：用于创建数组
- ! ， + ：对数组执行一些操作
- ( ， ) ：对操作进行分组
基础原理
- [] 可以用来创建数组，而 ![] 则可以返回 false
- 预定义的规则： 2 + true ，会转化为 2 + 1 ，最后得到 3
- 预定义的规则： 2 + "2" ，会转化为 2 + "2" ，最后得到 "22"
提取字母： ![] 可以获取 false ， ![] + [] 那可以获取 "false" 字符串，那么我们就可以通过下标获取其中的字母，比如： (![] + [])[1] 可以获取 false 字符串中第二位的字母 a
提取数字： ![] 可以获取 false ，由于 +false 可以获取 0 ，所以 +![] 就可以获取到 0 ；由于 +true 可以获取 1 ，所以 +!![] 就可以获取到 1 。这样依靠运算就可以获取更多其他数字
好了，有了这些基础基础知识之后，对于这个神奇的答案知道是怎么来的了吧？