dom是对象操纵方法？记得好像只是xml处理时使用的，html也使用到它？

也许就是把dom算成js的语法了，所以总觉得js的怪招层出不穷。。。。。
比如下面这个，是js执行了一个匿名函数？效果与执行一段代码没什么差别，为什么要做成匿名函数？？
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