请教一段js代码（不知道他是怎么写的）

<br> var currentTab = &#39;information&#39;;<br> var selectTab = function(index){ // 我这里不明白，function 函数名（）{} 是定义一个函数，但是他这个怎么<br> //直接就这样用，不明白啊<br> if(index == 1 ){<br> document.getElementById(&#39;information&#39;).style.display=&#39;&#39;;<br> document.getElementById(&#39;content&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;properties&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;voteshow&#39;).style.display=&#39;none&#39;;<br> info = &#39;current&#39;;<br> document.getElementById(&quot;cont&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;prop&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;vote&quot;).attributes[&#39;class&#39;].value = &#39;&#39;; <br> }<br> if(index == 2 &amp;&amp; currentTab!=&#39;content&#39;){<br> document.getElementById(&#39;information&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;content&#39;).style.display=&#39;&#39;;<br> document.getElementById(&#39;properties&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;voteshow&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&quot;info&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;cont&quot;).attributes[&#39;class&#39;].value = &#39;current&#39;;<br> document.getElementById(&quot;prop&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;vote&quot;).attributes[&#39;class&#39;].value = &#39;&#39;; </p> <p>}<br> if(index == 3 &amp;&amp; currentTab!=&#39;properties&#39;){<br> document.getElementById(&#39;information&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;content&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;properties&#39;).style.display=&#39;&#39;;<br> document.getElementById(&#39;voteshow&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&quot;info&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;cont&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;prop&quot;).attributes[&#39;class&#39;].value = &#39;current&#39;; <br> document.getElementById(&quot;vote&quot;).attributes[&#39;class&#39;].value = &#39;&#39;; </p> <p>}<br> if(index == 4 &amp;&amp; currentTab!=&#39;voteshow&#39;){<br> document.getElementById(&#39;information&#39;).style.display=&#39;none&#39;;<br> content.display=&#39;none&#39;;<br> document.getElementById(&#39;properties&#39;).style.display=&#39;none&#39;;<br> document.getElementById(&#39;voteshow&#39;).style.display=&#39;&#39;;<br> document.getElementById(&quot;info&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;cont&quot;).attributes[&#39;class&#39;].value = &#39;&#39;;<br> document.getElementById(&quot;prop&quot;).attributes[&#39;class&#39;].value = &#39;&#39;; <br> document.getElementById(&quot;vote&quot;).attributes[&#39;class&#39;].value = &#39;current&#39;; <br> }</p> <p>}</p> <p>1，var selectTab = function(index){ } <br> 我这里不明白，function 函数名（）{} 是定义一个函数，但是他这个怎么直接就这样用，不明白啊，求详解，<br> 2，另外这段代码要怎么样优化一下就看着舒服了<br> 3，style.display=&#39;none&#39;和style.display=&#39;&#39; 的区别是什么</p>

我一一对应回答如下:

1. var selectTab = function(index){} 等于 function selectTab(){}.
2. 优化一定可以, 要看到你的HTML和意图.
3. style.display='none' 是隐藏一个tag; style.display=''是显示一个tag.

打错了, 上面第一点改为: var selectTab = function(index){} 等于 function selectTab(index){}.