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<td WIDTH="74%" VALIGN="MIDDLE"><font FACE="宋体" LANG="ZH-CN" SIZE="4" COLOR="#ff0000"></font><b><font
FACE="System,黑体" LANG="ZH-CN" SIZE="4" COLOR="#ff0000">第</font><font
FACE="Verdana, arial" SIZE="4" COLOR="#ff0000">4</font><font FACE="System,黑体"
LANG="ZH-CN" SIZE="4" COLOR="#ff0000">页：再谈</font><font FACE="Verdana, arial"
SIZE="4" COLOR="#ff0000">While Loops</font></b><font FACE="宋体" LANG="ZH-CN"><br>
<!-- BYLINE --> </font><font FACE="System,黑体" LANG="ZH-CN" SIZE="2">作者：</font><a
HREF="mailto:thau@wired.com"><font FACE="宋体" LANG="ZH-CN" SIZE="2">Thau!</font></a><font
FACE="宋体" LANG="ZH-CN"> <!-- SEE ALSO LINKS --></font></td>
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<td WIDTH="74%" VALIGN="MIDDLE" BGCOLOR="#ffffff"><font FACE="System,黑体" LANG="ZH-CN"><hr>
<p>我们已见到了很多所请求的</font><font FACE="宋体" LANG="ZH-CN">X`S</font><font
FACE="System,黑体" LANG="ZH-CN">，现在复习一下：</p>
<p>第一步：请求</font><font FACE="宋体" LANG="ZH-CN">X`S</font><font
FACE="System,黑体" LANG="ZH-CN">的数目</font></td>
</tr>
<tr>
<td WIDTH="74%" VALIGN="TOP" BGCOLOR="#ffffff"><pre>
var width = prompt("How many x's would you like? (1-10 is good)","5");
</pre>
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<td WIDTH="74%" VALIGN="MIDDLE" BGCOLOR="#ffffff"><font FACE="System,黑体" LANG="ZH-CN">下一步，申报一些变量：</font><pre>
var a_line="";
var loop = 0;
</pre>
<font FACE="System,黑体" LANG="ZH-CN"><p>现在，关键之处：</p>
</font><pre>
while (loop < width)
{
a_line = a_line + "x";
loop=loop+1;
}
</pre>
<font FACE="System,黑体" LANG="ZH-CN"><p>即说：“当变量循环小于所请求的</font><font
FACE="宋体" LANG="ZH-CN">X`S</font><font FACE="System,黑体" LANG="ZH-CN">行宽时，在该行加入另一</font><font
FACE="宋体" LANG="ZH-CN">X</font><font FACE="System,黑体" LANG="ZH-CN">然后在循环值上加</font><font
FACE="宋体" LANG="ZH-CN">1</font><font FACE="System,黑体" LANG="ZH-CN">。”该循环将继续加一</font><font
FACE="宋体" LANG="ZH-CN">X</font><font FACE="System,黑体" LANG="ZH-CN">到该行并在循环值上加</font><font
FACE="宋体" LANG="ZH-CN">1</font><font FACE="System,黑体" LANG="ZH-CN">直到循环不在小于请求的行宽。请看下列源码分析：</font><font
SIZE="2"> </font><font FACE="System,黑体" LANG="ZH-CN"><dl>
<dt>第一次</dt>
<ul>
<ul>
</ul>
</ul>
<dd><ul>
<li>a_line = "" (because we initialized it to be "") </li>
</ul>
</dd>
<dd><ul>
<li>loop=0 (because we initialized it to be 0) </li>
</ul>
</dd>
<dd><ul>
<li>width=2 (because that's what the user asked for) </li>
</ul>
</dd>
<dd><ul>
<li>0 is less than 2 so </li>
</ul>
</dd>
<dd><ul>
<li>a_line = a_line + "x", so now a_line = "x" </li>
</ul>
</dd>
<dd><ul>
<li>loop=loop+1, so now loop = 1 </li>
</ul>
</dd>
</font><font FACE="System,黑体" LANG="ZH-CN">
<dt>返回循环：第二次</dt>
<ul>
<ul>
</ul>
</ul>
<dd><ul>
<li>loop=1 </li>
</ul>
</dd>
<dd><ul>
<li>width=2 </li>
</ul>
</dd>
<dd><ul>
<li>a_line = "x" </li>
</ul>
</dd>
<dd><ul>
<li>1 is less than 2 so </li>
</ul>
</dd>
<dd><ul>
<li>a_line = a_line + "x", so now a_line = "xx" </li>
</ul>
</dd>
<dd><ul>
<li>loop=loop+1, so now loop = 2 </li>
</ul>
</dd>
</font><font FACE="System,黑体" LANG="ZH-CN">
<dt>返回循环：第</font>3<font FACE="System,黑体" LANG="ZH-CN">次</dt>
<ul>
<ul>
</ul>
</ul>
<dd><ul>
<li>loop=2 </li>
</ul>
</dd>
<dd><ul>
<li>width=2 </li>
</ul>
</dd>
<dd><ul>
<li>a_line = "xx" </li>
</ul>
</dd>
<dd><ul>
<li>2 is NOT less than 2 so </li>
</ul>
</dd>
<dd><ul>
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