Menu implemented using two functions respectively_javascript skills

Menu made of css div: a main display layer, other lists are hidden, use js function to set the display and hiding of the list. Two functions are used respectively, and the effect of the function implementation is the same. One is the example in the "Css Dhtml Essence" book, and the other is the function I found.
Please help me see which function is useful! Does anyone have any other better ways to achieve this effect? Thanks! !

<font color="red"> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>Menu</title> <style type="text/css"> <!-- *{margin:0;padding:0;border:0;} body { background: #fff; font-size: 14px; font-family: "瀹</style></font>