找错了！！！！！

Question

          <script>
  var a = 1;
  if(a == 1)
   {
          </script>
              <tr>
                <td width="496" colspan="2" align="left" valign="top" height="40"><a href="z1.html">学而乐</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="middle" height="55"><a href="z2.html">我们年轻时唱过的歌</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="bottom" height="45"><a href="z3.html">游山玩水</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="bottom" height="55"><a href="z4.html">听妈妈讲那过去的事情</a></td>
              </tr>
 <script>
 }
             else if(a == 2){
             </script>               
              <tr>
                <td colspan="2" align="left" valign="bottom" height="55"><a href="z4.html">自然和历史之谜</a></a></td>
              </tr>
<script>}</script>

Answer 1

你这样嵌这script标签当然会报错了

Answer 2

<script>
var a = 1;
if(a == 1)
{
alert(1);
}else if(a == 2){
alert(2);
}
</script>就能看出来了，嵌着script标签会报错的，判断不出来也是正常的

Answer 3

JavaScript 是一种解释性语言（就是说，代码执行不进行预编译）。
一段一段的解析！
你这样会报脚本错误的

Answer 4

<script>
          var a = 1;
          if(a == 1)
              {
          document.write("
              <tr>
                <td width="496" colspan="2" align="left" valign="top" height="40"><a href="z1.html">学而乐</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="middle" height="55"><a href="z2.html">我们年轻时唱过的歌</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="bottom" height="45"><a href="z3.html">游山玩水</a></td>
              </tr>
              <tr>
                <td colspan="2" align="left" valign="bottom" height="55"><a href="z4.html">听妈妈讲那过去的事情</a></td>
              </tr>
             ");
             }
             else if(a == 2){
             document.write("         
              <tr>
                <td colspan="2" align="left" valign="bottom" height="55"><a href="z4.html">自然和历史之谜</a></a></td>
              </tr>
");}</script>