day4_4.html

javascript的学习文章

  <tr> 
    <td colspan="2">-<a href="../../1-teach/asp/index.html">ASP</a></td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-teach/php/index.html">PHP</a></td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-teach/java/index.htm">Java</a></td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-teach/vb/index.htm">VB</a></td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-teach/c/index.htm">C、C++</a></td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-backend/database/php_mysql/index.html">PHP/MySQL</a></td>
  </tr>
  <tr> 
    <td colspan="2"><a href="../../1-backend/cgi_perl/perl_beginner/index.html">-Perl</a> 
    </td>
  </tr>
  <tr> 
    <td colspan="2">-<a href="../../1-teach/other/index.htm">其它</a> </td>
  </tr>
  <tr> 
    <td colspan="2" bgcolor="#666699"> 
      <div align="center"><font color="#FFFFFF">更多教程</font></div>
    </td>
  </tr>
  <tr> 
    <td colspan="2" height="17"><a href="../../1hdml/index.html">-HDML</a></td>
  </tr>
  <tr> 
    <td colspan="2" height="23"><font face="宋体"><a href="../../1-backend/database/course/day1_1.html">-网络数据库</a></font></td>
  </tr>
  <tr> 
    <td colspan="2" height="14"><a href="../../1-backend/protocols/ping/index.html"><font face="arial, helvetica, sans-serif">Ping</font></a></td>
  </tr>
  <tr> 
    <td colspan="2" height="20"><a href="../../1-backend/cgi_perl/search_engine/index.html">-创建搜索引擎</a></td>
  </tr>
  <tr> 
    <td colspan="2" height="16">-<a href="../../1adobe/GoLive/index.html">Adobe GoLive</a></td>
  </tr>
  <tr> 
    <td colspan="2"><a href="../../1-backend/cgi_perl/templates/index.html">模板</a></td>
  </tr>
  <tr> 
    <td colspan="2" align="center" bgcolor="#666699"><font color="#FFFFFF">合作伙伴</font></td>
  </tr>
  <tr> 
    <td colspan="2" align="left">-<a href="http://www.5dmedia.com/" target="_blank">5D精英网</a></td>
  </tr>
  <tr align="center"> 
    <td colspan="2"> <img src="../../Library/front_monkey.gif" width="59" height="68"></td>
  </tr>
  </tbody> 
</table>
<br><!-- #EndLibraryItem --></td>
      <!-- End of headlines (column 1: left column) --> <!-- Gutter between columns 1 and 2 --> 
      <td width="10" height="794"><img src="http://www.sohu.com/images/pixel.gif" width=10></td>
      <!-- Search box and directories (columns 2 and 3: middle columns, combined into one) --> 
      <td align=center valign=top width="558"> 
        <div align="left"><!-- #BeginEditable "1" --> 
<title>JavaScrip教程</title>
 <strong><font face="宋体" size="3">第四页：</font><font size="3">再谈<font face="宋体">WHILE</font>循环</font></strong> 
      <p><font size="2"></font><font size="3">我们已见到了很多所请求的<font face="宋体">X`S</font>，现在复习一下：</font></p>
      <font size="3"> 
      <p>第一步：请求<font face="宋体">X`S</font>的数目</p>
      </font> 
      <p><font face="宋体">var width = prompt(&quot;How many x's would you like? 
        (1-10 is<br>
        good)&quot;,&quot;5&quot;);<br>
        </font></p>
      <p><font face="宋体" size="3">下一步，申报一些变量：</font>
      <ul>
        <pre><font face="宋体">
var a_line=&quot;&quot;;

var loop = 0;

</font></pre>
      </ul>
      <p><font face="宋体" size="3">现在，关键之处：</font>
      <ul>
        <pre><font face="宋体">

while (loop &lt; width)

{

	a_line = a_line + &quot;x&quot;;

	loop=loop+1;

}

</font></pre>
      </ul>
      <p><font face="宋体" size="3">即说：“当变量循环小于所请求的X`S行宽时，在该行加入另一<br>
        X然后在循环值上加1。”该循环将继续加一X到该行并在循环值<br>
        上加1直到循环不在小于请求的行宽。请看下列源码分析：</font>
      <dl> 
        <dt><font face="宋体" size="3">第一次</font></dt>
        <dd> 
          <ul>
            <li><font face="宋体">a_line = &quot;&quot; (because we initialized 
              it to be &quot;&quot;) </font></li>
            <li><font face="宋体">loop=0 (because we initialized it to be 0) </font></li>
            <li><font face="宋体">width=2 (because that's what the user asked for) 
              </font></li>
            <li><font face="宋体">0 is less than 2 so </font></li>
            <li><font face="宋体">a_line = a_line + &quot;x&quot;, so now a_line 
              = &quot;x&quot; </font></li>
            <li><font face="宋体">loop=loop+1, so now loop = 1 </font></li>
          </ul>
        </dd>
        <dt><font face="宋体" size="3">返回循环：第二次</font></dt>
        <dd> 
          <ul>
            <li><font face="宋体">loop=1 </font></li>
            <li><font face="宋体">width=2 </font></li>
            <li><font face="宋体">a_line = &quot;x&quot; </font></li>
            <li><font face="宋体">1 is less than 2 so </font></li>
            <li><font face="宋体">a_line = a_line + &quot;x&quot;, so now a_line 
              = &quot;xx&quot; </font></li>
            <li><font face="宋体">loop=loop+1, so now loop = 2 </font></li>
          </ul>
        </dd>
        <dt><font face="宋体" size="3">返回循环：第3次</font></dt>
        <font size="2"> 
        <dd> 
          <ul>
            <li><font face="宋体">loop=2 </font></li>
            <li><font face="宋体">width=2 </font></li>
            <li><font face="宋体">a_line = &quot;xx&quot; </font></li>
            <li><font face="宋体">2 is NOT less than 2 so </font></li>
            <li><font face="宋体">fall out of the loop and do what follows </font></li>
          </ul>
        </dd>
        </font> </dl>
      <p align="JUSTIFY"><font size="3">随后是：</font></p>
      <ul>
        <pre>
      <font size="2"></font><font size="3">
<font face="宋体">alert(a_line);

</font></font></pre>
        <p align="JUSTIFY"> <font size="2"></font><font size="3">启动一个警告对话框。</font></p>
        <p align="JUSTIFY"> <font size="3">这种循环运用的如此普遍以至于程序员们开发了一些简便<br>
          方式，条件循环可写成这样：</font></p>
      </ul>
      <ul>
        <pre>
      <font size="2"></font><font size="3">
<font face="宋体">while (loop &lt; width)

{

	a_line += &quot;x&quot;;  //this was a_line = a_line + &quot;x&quot;;

	loop++;         //this was loop=loop+1;

}

</font></font></pre>
      </ul>
      <p> <font size="2"></font><font face="宋体" size="3">首行，“x”，表示“本身加x”。若已有a_number=5，那么可<br>
        写成，a_number+=3，即是说：a_number=a_number+3。程序员<br>
        就是这么偷懒的。</font></p>
      <p align="JUSTIFY"> <font size="2"></font><font face="宋体" size="2">下行，</font><font size="3" face="宋体">loop++，意味着“自身加1”。于是loop++即为：<br>
        loop=loop=1。它也可写成loop+=1。这样偷懒行为非常有效。</font></p>
      <p align="JUSTIFY"> <font size="2"></font><font size="3" face="宋体">就象不止一种方式在一个数上加</font><font size="3"><font face="宋体">1</font>一样，也有不止一种方法来写<br>
        一个循环。<font face="宋体">While</font>循环不是唯一的循环模式，另一流行的循环<br>
        是<font face="宋体"><a href="day4_5.html">for循环</a>。</font></font></p>
      <p align="left"><font face="宋体" size="3" color="#000000"><strong>JavaScript教程</strong></font><font color="#FF0000" face="宋体" size="3"><br>
        </font><font size="3" color="#FF0000">第一页</font><font size="2" face="宋体"> 
        </font><a href="day4_4.html"><font size="3">第四课介绍</font></a><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第二页</font> <a href="day4_2.html">循环介绍</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第三页</font> <a href="day4_3.html">循环的密码</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第四页</font> 再谈<font face="宋体">WHILE</font>循环</font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第五页</font> <a href="day4_5.html">For循环</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第六页</font> <a href="day4_6.html">嵌套循环</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第七页</font> <a href="day4_7.html">循环练习</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第八页</font> <a href="day4_8.html">数组</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第九页</font> <a href="day4_9.html">数组和循环</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第十页</font> <a href="day4_10.html">文件目标模块中的数组</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第十一页</font> <a href="day4_11.html">函数</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第十二页</font> <a href="day4_12.html">无参数函数</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第十三页</font> <a href="day4_13.html">参数及返回值</a></font><font size="2"><br>
        </font><font size="3"><font color="#FF0000">第十四页</font> <a href="day4_14.html">多于一个参数的函数</a></font></p>
      <p align="left"><font face="宋体" size="3">[<a href="index.html">第1课</a>][<a href="day2_1.html">第2课</a>][<a href="day3_1.html">第3课</a>][第4课][<a href="day5_1.html">第5课</a>]</font></p>
      <!-- #EndEditable --></div>
      </td>
      <!-- End of search box and directories (columns 2 and 3: middle columns, combined into one) --> 
      <!-- Gutter between columns 3 and 4 --> <!-- Other stuff (column 4: right column) --> 
      <!-- End of other stuff (column 4: right column) --> </tr>
  </table>
<!-- End of table surrounding page contents -->

  <hr noshade size=1 width=700>
 <span class=eng><br>
  Copyright (C) 1998-2000 Internet Technologies China.&nbsp; All rights reserved. 
  </span> 
</center>
</body>
<!-- #EndTemplate --></html>