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CONTENT="Thau's JavaScript Tutorial: Day 1: Not only does Thau give the JavaScript skinny, but he'll have you writing your first script by the end of the day.">
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<td WIDTH="68%" VALIGN="MIDDLE"><font FACE="宋體" LANG="ZH-CN" SIZE="4" COLOR="#ff0000"></font><font
FACE="System,黑體" LANG="ZH-CN" SIZE="5" COLOR="#ff0000"><b>第3頁：循環(huán)密碼</b></font><font
FACE="System,黑體" LANG="ZH-CN"><br>
<!-- BYLINE --> </font><font FACE="System,黑體" LANG="ZH-CN" SIZE="2">作者：</font><a
HREF="mailto:thau@wired.com"><font FACE="宋體" LANG="ZH-CN" SIZE="2">Thau!</font></a><font
FACE="宋體" LANG="ZH-CN"> <!-- SEE ALSO LINKS --></font></td>
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<td WIDTH="68%" VALIGN="TOP" BGCOLOR="#ffffff"><font FACE="System,黑體" LANG="ZH-CN"
SIZE="2"><p ALIGN="JUSTIFY">那就是密碼！</p>
<p ALIGN="JUSTIFY">讓我們逐行地來研究這個例子，如果你想看整個答案，可以查看源碼。</p>
<p ALIGN="JUSTIFY">在這個典型的</font><font FACE="宋體" LANG="ZH-CN">Java script </font><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2">序言之后，我們從雙變量申報開始：</p>
<blockquote ALIGN="JUSTIFY">
<p><br>
<br>
</font><font FACE="Verdana, arial" SIZE="2">var password="pass the wrench";<br>
<br>
var answer;<br>
</font></p>
</blockquote>
<font FACE="System,黑體" LANG="ZH-CN" SIZE="2"><p ALIGN="JUSTIFY">這里我們定義該密碼作為一個字符串，我們申報一個稱為</font><font
FACE="宋體" LANG="ZH-CN">answer </font><font FACE="System,黑體" LANG="ZH-CN">的變量。你將理解為什么我們不得不立即申報一個</font><font
FACE="宋體" LANG="ZH-CN">answer</font><font FACE="System,黑體" LANG="ZH-CN" SIZE="2">。下面幾行是非常重要的：</p>
<blockquote ALIGN="JUSTIFY">
<p><br>
<br>
</font><font FACE="Verdana, arial" SIZE="2">while (answer != password) <br>
<br>
{<br>
<br>
answer = prompt("What's the woyd?","");<br>
<br>
}<br>
</font></p>
</blockquote>
<font FACE="System,黑體" LANG="ZH-CN" SIZE="2"><p ALIGN="JUSTIFY">這是一個</font><font
FACE="宋體" LANG="ZH-CN">while</font><font FACE="System,黑體" LANG="ZH-CN">循環(huán)。</font><font
FACE="宋體" LANG="ZH-CN">while </font><font FACE="System,黑體" LANG="ZH-CN" SIZE="2">循環(huán)的一般格式為：</p>
<blockquote ALIGN="JUSTIFY">
<p><br>
<br>
</font><font FACE="Verdana, arial" SIZE="2">while (some test is true)<br>
<br>
{<br>
<br>
do the stuff inside the curly braces<br>
<br>
}<br>
</font></p>
</blockquote>
<font FACE="System,黑體" LANG="ZH-CN"><p ALIGN="JUSTIFY">上述幾行表明：“當</font><font
FACE="宋體" LANG="ZH-CN">answer</font><font FACE="System,黑體" LANG="ZH-CN">不等價于</font><font
FACE="宋體" LANG="ZH-CN">Password</font><font FACE="System,黑體" LANG="ZH-CN">時，執(zhí)行提示命令。”這一循環(huán)將持續(xù)地執(zhí)行波形括號內的語句直至測試失敗。在使用者輸入的單詞與密碼一致</font><font
FACE="宋體" LANG="ZH-CN">(</font><font FACE="System,黑體" LANG="ZH-CN">即</font><font
FACE="宋體" LANG="ZH-CN">Pass the wrench)</font><font FACE="System,黑體" LANG="ZH-CN"
SIZE="2">的情況下，測試必將失敗。</p>
</font><font FACE="System,黑體" LANG="ZH-CN"><p ALIGN="JUSTIFY">由于在對一個未申報的變量執(zhí)行一個如</font><font
FACE="宋體" LANG="ZH-CN">(answer!=password)</font><font FACE="System,黑體"
LANG="ZH-CN">的測試時，在某些瀏覽器上會產(chǎn)生錯誤，所以我們必須申報</font><font
FACE="宋體" LANG="ZH-CN">answer</font><font FACE="System,黑體" LANG="ZH-CN">。由于在</font><font
FACE="宋體" LANG="ZH-CN">while</font><font FACE="System,黑體" LANG="ZH-CN">循環(huán)中將通過提示方案對</font><font
FACE="宋體" LANG="ZH-CN">answer</font><font FACE="System,黑體" LANG="ZH-CN">賦值，在我們第一次進行循環(huán)中，</font><font
FACE="宋體" LANG="ZH-CN">answer</font><font FACE="System,黑體" LANG="ZH-CN" SIZE="2">將沒有數(shù)值。提前定義它并設定其處始值為“”。</p>
</font><font FACE="System,黑體" LANG="ZH-CN"><p ALIGN="JUSTIFY">由于不定義循環(huán)經(jīng)常地使用，循環(huán)經(jīng)常用來執(zhí)行一組語句某一特定的次數(shù)。這里用<a
HREF="tutorial4_page4.htm">另一個循環(huán)</a>來演示如何作這項工作。</p>
<p><!-- PAGE X LINKS --><!-- this stuff checks if there are more pages in this story. if so, we'll
suck out the titles of those pages and build links. Right now, the maximum is
15 pages. -->第</font><font FACE="宋體" LANG="ZH-CN">1</font><font FACE="System,黑體"
LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4.htm"><font FACE="System,黑體" LANG="ZH-CN">第四課介紹</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- PAGE X LINKS --><!-- this stuff checks if there are more pages in this story. if so, we'll
suck out the titles of those pages and build links. Right now, the maximum is 15 pages. --><!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">2</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page2.htm"><font FACE="System,黑體" LANG="ZH-CN">循環(huán)介紹</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">3</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page3.htm"><font FACE="System,黑體" LANG="ZH-CN">循環(huán)的密碼</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">4</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page4.htm"><font FACE="System,黑體" LANG="ZH-CN">再談</font><font
FACE="宋體" LANG="ZH-CN">WHILE</font><font FACE="System,黑體" LANG="ZH-CN">循環(huán)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">5</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page5.htm"><font FACE="宋體" LANG="ZH-CN">For </font><font
FACE="System,黑體" LANG="ZH-CN">循環(huán)</font></a><font FACE="System,黑體" LANG="ZH-CN"
SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">6</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page6.htm"><font FACE="System,黑體" LANG="ZH-CN">嵌套循環(huán)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">7</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page7.htm"><font FACE="System,黑體" LANG="ZH-CN">循環(huán)練習</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">8</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page8.htm"><font FACE="System,黑體" LANG="ZH-CN">數(shù)組</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">9</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page9.htm"><font FACE="System,黑體" LANG="ZH-CN">數(shù)組和循環(huán)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">10</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">:</font><a
HREF="tutorial4_page10.html"><font FACE="System,黑體" LANG="ZH-CN">文件目標模塊中的數(shù)組</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">11</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page11.htm"><font FACE="System,黑體" LANG="ZH-CN">函數(shù)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">12</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page12.html"><font FACE="System,黑體" LANG="ZH-CN">無參數(shù)函數(shù)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">13</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page13.htm"><font FACE="System,黑體" LANG="ZH-CN">參數(shù)及返回值</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
<!-- this is a mini-template that formats each pageX link. So, if a story
has 15 pages, we need to generate 15 links to it. This is how each one
will look... --> </font><font FACE="System,黑體" LANG="ZH-CN">第</font><font FACE="宋體" LANG="ZH-CN">14</font><font
FACE="System,黑體" LANG="ZH-CN">頁</font><font FACE="宋體" LANG="ZH-CN" SIZE="2">: </font><a
HREF="tutorial4_page14.htm"><font FACE="System,黑體" LANG="ZH-CN">多于一個參數(shù)的函數(shù)</font></a><font
FACE="System,黑體" LANG="ZH-CN" SIZE="2"><br>
</font><font FACE="System,黑體" LANG="ZH-CN"></p>
<p><br>
</p>
</font><font FACE="System,黑體" LANG="ZH-CN" SIZE="2"><p><br>
<!-- AUTHOR TAGLINE --> </font></td>
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