这篇介绍javascript方面的日志，我在是Clang上看到的。作者介绍挺全面的，所以转载过来让感兴趣的朋友看一下。呵呵～～～
有些时候你精通一门语言，但是会发现你其实整天在和其它语言打交道，也许你以为这些微不足道，不至于影响你的开发进度，但恰恰是这些你不重视的东西会浪费你很多时间，我一直以为我早在几年前就已经精通JavaScript了，直到目前，我才越来越觉得JavaScript远比我想象的复杂和强大，我开始崇拜它，
趁着节日的空隙，把有关JavaScript的方法和技巧整理下，让每个在为JavaScript而烦恼的人明白，JavaScript就这么回事！并希望JavaScript还可以成为你的朋友，让你豁然开朗，在项目中更好的应用～
适合阅读范围：对JavaScript一无所知～离精通只差一步之遥的人
基础知识：HTML
JavaScript就这么回事1：基础知识
1 创建脚本块
1: <script language=”JavaScript” >
2: JavaScript code goes here
3: </script >
2 隐藏脚本代码
1: <script language=”JavaScript” >
2: <!--
3: document.write(“Hello”);
4: // -- >
5: </script >
在不支持JavaScript的浏览器中将不执行相关代码
3 浏览器不支持的时候显示
1: <noscript >
2: Hello to the non-JavaScript browser.
3: </noscript >
4 链接外部脚本文件
1: <script language=”JavaScript” src= "/”filename.js "” > </script >
5 注释脚本
1: // This is a comment
2: document.write(“Hello”); // This is a comment
3: /*
4: All of this
5: is a comment
6: */
6 输出到浏览器
1: document.write(“ <strong >Hello </strong >”);
7 定义变量
1: var myVariable = “some value”;
8 字符串相加
1: var myString = “String1” + “String2”;
9 字符串搜索
1: <script language=”JavaScript” >
2: <!--
3: var myVariable = “Hello there”;
4: var therePlace = myVariable.search(“there”);
5: document.write(therePlace);
6: // -- >
7: </script >
10 字符串替换
1: thisVar.replace(“Monday”,”Friday”);
11 格式化字串
1: <script language=”JavaScript” >
2: <!--
3: var myVariable = “Hello there”;
4: document.write(myVariable.big() + “ <br >”);
5: document.write(myVariable.blink() + “ <br >”);
6: document.write(myVariable.bold() + “ <br >”);
7: document.write(myVariable.fixed() + “ <br >”);
8: document.write(myVariable.fontcolor(“red”) + “ <br >”);
9: document.write(myVariable.fontsize(“18pt”) + “ <br >”);
10: document.write(myVariable.italics() + “ <br >”);
11: document.write(myVariable.small() + “ <br >”);
12: document.write(myVariable.strike() + “ <br >”);
13: document.write(myVariable.sub() + “ <br >”);
14: document.write(myVariable.sup() + “ <br >”);
15: document.write(myVariable.toLowerCase() + “ <br >”);
16: document.write(myVariable.toUpperCase() + “ <br >”);
17:
18: var firstString = “My String”;
19: var finalString = firstString.bold().toLowerCase().fontcolor(“red”);
20: // -- >
21: </script >
12 创建数组
1: <script language=”JavaScript” >
2: <!--
3: var myArray = new Array(5);
4: myArray[0] = “First Entry”;
5: myArray[1] = “Second Entry”;
6: myArray[2] = “Third Entry”;
7: myArray[3] = “Fourth Entry”;
8: myArray[4] = “Fifth Entry”;
9: var anotherArray = new Array(“First Entry”,”Second Entry”,”Third Entry”,”Fourth Entry”,”Fifth Entry”);
10: // -- >
11: </script >
13 数组排序
1: <script language=”JavaScript” >
2: <!--
3: var myArray = new Array(5);
4: myArray[0] = “z”;
5: myArray[1] = “c”;
6: myArray[2] = “d”;
7: myArray[3] = “a”;
8: myArray[4] = “q”;
9: document.write(myArray.sort());
10: // -- >
11: </script >
14 分割字符串
1: <script language=”JavaScript” >
2: <!--
3: var myVariable = “a,b,c,d”;
4: var stringArray = myVariable.split(“,”);
5: document.write(stringArray[0]);
6: document.write(stringArray[1]);
7: document.write(stringArray[2]);
8: document.write(stringArray[3]);
9: // -- >
10: </script >
15 弹出警告信息
1: <script language=”JavaScript” >
2: <!--
3: window.alert(“Hello”);
4: // -- >
5: </script >
16 弹出确认框
1: <script language=”JavaScript” >
2: <!--
3: var result = window.confirm(“Click OK to continue”);
4: // -- >
5: </script >
17 定义函数
1: <script language=”JavaScript” >
2: <!--
3: function multiple(number1,number2) {
4: var result = number1 * number2;
5: return result;
6: }
7: // -- >
8: </script >
18 调用JS函数
1: <a href=”#” onClick=”functionName()” >Link text </a >
2: <a href= "/”javascript:functionName "()” >Link text </a >
19 在页面加载完成后执行函数
1: <body onLoad=”functionName();” >
2: Body of the page
3: </body >
20 条件判断
1: <script >
2: <!--
3: var userChoice = window.confirm(“Choose OK or Cancel”);
4: var result = (userChoice == true) ? “OK” : “Cancel”;
5: document.write(result);
6: // -- >
7: </script >
21 指定次数循环
1: <script >
2: <!--
3: var myArray = new Array(3);
4: myArray[0] = “Item 0”;
5: myArray[1] = “Item 1”;
6: myArray[2] = “Item 2”;
7: for (i = 0; i < myArray.length; i++) {
8: document.write(myArray[i] + “ <br >”);
9: }
10: // -- >
11: </script >
22 设定将来执行
1: <script >
2: <!--
3: function hello() {
4: window.alert(“Hello”);
5: }
6: window.setTimeout(“hello()”,5000);
7: // -- >
8: </script >
23 定时执行函数
1: <script >
2: <!--
3: function hello() {
4: window.alert(“Hello”);
5: window.setTimeout(“hello()”,5000);
6: }
7: window.setTimeout(“hello()”,5000);
8: // -- >
9: </script >
24 取消定时执行
1: <script >
2: <!--
3: function hello() {
4: window.alert(“Hello”);
5: }
6: var myTimeout = window.setTimeout(“hello()”,5000);
7: window.clearTimeout(myTimeout);
8: // -- >
9: </script >
25 在页面卸载时候执行函数
1: <body onUnload=”functionName();” >
2: Body of the page
3: </body >
JavaScript就这么回事2：浏览器输出
26 访问document对象
1: <script language=”JavaScript” >
2: var myURL = document.URL;
3: window.alert(myURL);
4: </script >
27 动态输出HTML
1: <script language=”JavaScript” >
2: document.write(“ <p >Here’s some information about this document: </p >”);
3: document.write(“ <ul >”);
4: document.write(“ <li >Referring Document: “ + document.referrer + “ </li >”);
5: document.write(“ <li >Domain: “ + document.domain + “ </li >”);
6: document.write(“ <li >URL: “ + document.URL + “ </li >”);
7: document.write(“ </ul >”);
8: </script >
28 输出换行
1: document.writeln(“ <strong >a </strong >”);
2: document.writeln(“b”);
29 输出日期
1: <script language=”JavaScript” >
2: var thisDate = new Date();
3: document.write(thisDate.toString());
4: </script >
30 指定日期的时区
1: <script language=”JavaScript” >
2: var myOffset = -2;
3: var currentDate = new Date();
4: var userOffset = currentDate.getTimezoneOffset()/60;
5: var timeZoneDifference = userOffset - myOffset;
6: currentDate.setHours(currentDate.getHours() + timeZoneDifference);
7: document.write(“The time and date in Central Europe is: “ + currentDate.toLocaleString());
8: </script >
31 设置日期输出格式
1: <script language=”JavaScript” >
2: var thisDate = new Date();
3: var thisTimeString = thisDate.getHours() + “:” + thisDate.getMinutes();
4: var thisDateString = thisDate.getFullYear() + “/” + thisDate.getMonth() + “/” + thisDate.getDate();
5: document.write(thisTimeString + “ on “ + thisDateString);
6: </script >
32 读取URL参数
1: <script language=”JavaScript” >
2: var urlParts = document.URL.split(“?”);
3: var parameterParts = urlParts[1].split(“&amp;”);
4: for (i = 0; i < parameterParts.length; i++) {
5: var pairParts = parameterParts[i].split(“=”);
6: var pairName = pairParts[0];
7: var pairValue = pairParts[1];
8: document.write(pairName + “ ：“ +pairValue );
9: }
10: </script >
你还以为HTML是无状态的么？
33 打开一个新的document对象
1: <script language=”JavaScript” >
2: function newDocument() {
3: document.open();
4: document.write(“ <p >This is a New Document. </p >”);
5: document.close();
6: }
7: </script >
34 页面跳转
1: <script language=”JavaScript” >
2: window.location = “http://www.liu21st.com/”;
3: </script >
35 添加网页加载进度窗口
1: <html >
2: <head >
3: <script language= &amp;apos;javaScript &amp;apos; >
4: var placeHolder = window.open( &amp;apos;holder.html &amp;apos;, &amp;apos;placeholder &amp;apos;, &amp;apos;width=200,height=200 &amp;apos;);
5: </script >
6: <title >The Main Page </title >
7: </head >
8: <body onLoad= &amp;apos;placeHolder.close() &amp;apos; >
9: <p >This is the main page </p >
10: </body >
11: </html >
26 访问document对象
1: <script language=”JavaScript” >
2: var myURL = document.URL;
3: window.alert(myURL);
4: </script >
27 动态输出HTML
1: <script language=”JavaScript” >
2: document.write(“ <p >Here’s some information about this document: </p >”);
3: document.write(“ <ul >”);
4: document.write(“ <li >Referring Document: “ + document.referrer + “ </li >”);
5: document.write(“ <li >Domain: “ + document.domain + “ </li >”);
6: document.write(“ <li >URL: “ + document.URL + “ </li >”);
7: document.write(“ </ul >”);
8: </script >
28 输出换行
1: document.writeln(“ <strong >a </strong >”);
2: document.writeln(“b”);
29 输出日期
1: <script language=”JavaScript” >
2: var thisDate = new Date();
3: document.write(thisDate.toString());
4: </script >
30 指定日期的时区
1: <script language=”JavaScript” >
2: var myOffset = -2;
3: var currentDate = new Date();
4: var userOffset = currentDate.getTimezoneOffset()/60;
5: var timeZoneDifference = userOffset - myOffset;
6: currentDate.setHours(currentDate.getHours() + timeZoneDifference);
7: document.write(“The time and date in Central Europe is: “ + currentDate.toLocaleString());
8: </script >
31 设置日期输出格式
1: <script language=”JavaScript” >
2: var thisDate = new Date();
3: var thisTimeString = thisDate.getHours() + “:” + thisDate.getMinutes();
4: var thisDateString = thisDate.getFullYear() + “/” + thisDate.getMonth() + “/” + thisDate.getDate();
5: document.write(thisTimeString + “ on “ + thisDateString);
6: </script >
32 读取URL参数
1: <script language=”JavaScript” >
2: var urlParts = document.URL.split(“?”);
3: var parameterParts = urlParts[1].split(“&amp;”);
4: for (i = 0; i < parameterParts.length; i++) {
5: var pairParts = parameterParts[i].split(“=”);
6: var pairName = pairParts[0];
7: var pairValue = pairParts[1];
8: document.write(pairName + “ ：“ +pairValue );
9: }
10: </script >
你还以为HTML是无状态的么？
33 打开一个新的document对象
1: <script language=”JavaScript” >
2: function newDocument() {
3: document.open();
4: document.write(“ <p >This is a New Document. </p >”);
5: document.close();
6: }
7: </script >
34 页面跳转
1: <script language=”JavaScript” >
2: window.location = “http://www.liu21st.com/”;
3: </script >
35 添加网页加载进度窗口
1: <html >
2: <head >
3: <script language= &amp;apos;javaScript &amp;apos; >
4: var placeHolder = window.open( &amp;apos;holder.html &amp;apos;, &amp;apos;placeholder &amp;apos;, &amp;apos;width=200,height=200 &amp;apos;);
5: </script >
6: <title >The Main Page </title >
7: </head >
8: <body onLoad= &amp;apos;placeHolder.close() &amp;apos; >
9: <p >This is the main page </p >
10: </body >
11: </html >
JavaScript就这么回事3：图像
36 读取图像属性
1: <img src= "/”image1.jpg "” name=”myImage” >
2: <a href=”# ” onClick=”window.alert(document.myImage.width)” >Width </a >
3:
37 动态加载图像
1: <script language=”JavaScript” >
2: myImage = new Image;
3: myImage.src = “Tellers1.jpg”;
4: </script >
38 简单的图像替换
1: <script language=”JavaScript” >
2: rollImage = new Image;
3: rollImage.src = “rollImage1.jpg”;
4: defaultImage = new Image;
5: defaultImage.src = “image1.jpg”;
6: </script >
7: <a href= "/”myUrl "” onMouseOver=”document.myImage.src = rollImage.src;”
8: onMouseOut=”document.myImage.src = defaultImage.src;” >
9: <img src= "/”image1.jpg "” name=”myImage” width=100 height=100 border=0 >
39 随机显示图像
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = “image1.jpg”;
4: imageList[1] = “image2.jpg”;
5: imageList[2] = “image3.jpg”;
6: imageList[3] = “image4.jpg”;
7: var imageChoice = Math.floor(Math.random() * imageList.length);
8: document.write(‘ <img src=”’ + imageList[imageChoice] + ‘“ >’);
9: </script >
40 函数实现的图像替换
1: <script language=”JavaScript” >
2: var source = 0;
3: var replacement = 1;
4: function createRollOver(originalImage,replacementImage) {
5: var imageArray = new Array;
6: imageArray[source] = new Image;
7: imageArray[source].src = originalImage;
8: imageArray[replacement] = new Image;
9: imageArray[replacement].src = replacementImage;
10: return imageArray;
11: }
12: var rollImage1 = createRollOver(“image1.jpg”,”rollImage1.jpg”);
13: </script >
14: <a href=”#” onMouseOver=”document.myImage1.src = rollImage1[replacement].src;”
15: onMouseOut=”document.myImage1.src = rollImage1[source].src;” >
16: <img src= "/”image1.jpg "” width=100 name=”myImage1” border=0 >
17: </a >
41 创建幻灯片
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = new Image;
4: imageList[0].src = “image1.jpg”;
5: imageList[1] = new Image;
6: imageList[1].src = “image2.jpg”;
7: imageList[2] = new Image;
8: imageList[2].src = “image3.jpg”;
9: imageList[3] = new Image;
10: imageList[3].src = “image4.jpg”;
11: function slideShow(imageNumber) {
12: document.slideShow.src = imageList[imageNumber].src;
13: imageNumber += 1;
14: if (imageNumber < imageList.length) {
15: window.setTimeout(“slideShow(“ + imageNumber + “)”,3000);
16: }
17: }
18: </script >
19: </head >
20: <body onLoad=”slideShow(0)” >
21: <img src= "/”image1.jpg "” width=100 name=”slideShow” >
42 随机广告图片
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = “image1.jpg”;
4: imageList[1] = “image2.jpg”;
5: imageList[2] = “image3.jpg”;
6: imageList[3] = “image4.jpg”;
7: var urlList = new Array;
8: urlList[0] = “http://some.host/”;
9: urlList[1] = “http://another.host/”;
10: urlList[2] = “http://somewhere.else/”;
11: urlList[3] = “http://right.here/”;
12: var imageChoice = Math.floor(Math.random() * imageList.length);
13: document.write(‘ <a href=”’ + urlList[imageChoice] + ‘“ > <img src=”’ + imageList[imageChoice] + ‘“ > </a >’);
14: </script >
36 读取图像属性
1: <img src= "/”image1.jpg "” name=”myImage” >
2: <a href=”# ” onClick=”window.alert(document.myImage.width)” >Width </a >
3:
37 动态加载图像
1: <script language=”JavaScript” >
2: myImage = new Image;
3: myImage.src = “Tellers1.jpg”;
4: </script >
38 简单的图像替换
1: <script language=”JavaScript” >
2: rollImage = new Image;
3: rollImage.src = “rollImage1.jpg”;
4: defaultImage = new Image;
5: defaultImage.src = “image1.jpg”;
6: </script >
7: <a href= "/”myUrl "” onMouseOver=”document.myImage.src = rollImage.src;”
8: onMouseOut=”document.myImage.src = defaultImage.src;” >
9: <img src= "/”image1.jpg "” name=”myImage” width=100 height=100 border=0 >
39 随机显示图像
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = “image1.jpg”;
4: imageList[1] = “image2.jpg”;
5: imageList[2] = “image3.jpg”;
6: imageList[3] = “image4.jpg”;
7: var imageChoice = Math.floor(Math.random() * imageList.length);
8: document.write(‘ <img src=”’ + imageList[imageChoice] + ‘“ >’);
9: </script >
40 函数实现的图像替换
1: <script language=”JavaScript” >
2: var source = 0;
3: var replacement = 1;
4: function createRollOver(originalImage,replacementImage) {
5: var imageArray = new Array;
6: imageArray[source] = new Image;
7: imageArray[source].src = originalImage;
8: imageArray[replacement] = new Image;
9: imageArray[replacement].src = replacementImage;
10: return imageArray;
11: }
12: var rollImage1 = createRollOver(“image1.jpg”,”rollImage1.jpg”);
13: </script >
14: <a href=”#” onMouseOver=”document.myImage1.src = rollImage1[replacement].src;”
15: onMouseOut=”document.myImage1.src = rollImage1[source].src;” >
16: <img src= "/”image1.jpg "” width=100 name=”myImage1” border=0 >
17: </a >
41 创建幻灯片
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = new Image;
4: imageList[0].src = “image1.jpg”;
5: imageList[1] = new Image;
6: imageList[1].src = “image2.jpg”;
7: imageList[2] = new Image;
8: imageList[2].src = “image3.jpg”;
9: imageList[3] = new Image;
10: imageList[3].src = “image4.jpg”;
11: function slideShow(imageNumber) {
12: document.slideShow.src = imageList[imageNumber].src;
13: imageNumber += 1;
14: if (imageNumber < imageList.length) {
15: window.setTimeout(“slideShow(“ + imageNumber + “)”,3000);
16: }
17: }
18: </script >
19: </head >
20: <body onLoad=”slideShow(0)” >
21: <img src= "/”image1.jpg "” width=100 name=”slideShow” >
42 随机广告图片
1: <script language=”JavaScript” >
2: var imageList = new Array;
3: imageList[0] = “image1.jpg”;
4: imageList[1] = “image2.jpg”;
5: imageList[2] = “image3.jpg”;
6: imageList[3] = “image4.jpg”;
7: var urlList = new Array;
8: urlList[0] = “http://some.host/”;
9: urlList[1] = “http://another.host/”;
10: urlList[2] = “http://somewhere.else/”;
11: urlList[3] = “http://right.here/”;
12: var imageChoice = Math.floor(Math.random() * imageList.length);
13: document.write(‘ <a href=”’ + urlList[imageChoice] + ‘“ > <img src=”’ + imageList[imageChoice] + ‘“ > </a >’);
14: </script >
JavaScript就这么回事4：表单
还是先继续写完JS就这么回事系列吧～
43 表单构成
1: <form method=”post” action=”target.html” name=”thisForm” >
2: <input type=”text” name=”myText” >
3: <select name=”mySelect” >
4: <option value=”1” >First Choice </option >
5: <option value=”2” >Second Choice </option >
6: </select >
7: <br >
8: <input type=”submit” value=”Submit Me” >
9: </form >
44 访问表单中的文本框内容
1: <form name=”myForm” >
2: <input type=”text” name=”myText” >
3: </form >
4: <a href= &amp;apos;# &amp;apos; onClick= &amp;apos;window.alert(document.myForm.myText.value); &amp;apos; >Check Text Field </a >
45 动态复制文本框内容
1: <form name=”myForm” >
2: Enter some Text: <input type=”text” name=”myText” > <br >
3: Copy Text: <input type=”text” name=”copyText” >
4: </form >
5: <a href=”#” onClick=”document.myForm.copyText.value =
6: document.myForm.myText.value;” >Copy Text Field </a >
46 侦测文本框的变化
1: <form name=”myForm” >
2: Enter some Text: <input type=”text” name=”myText” onChange=”alert(this.value);” >
3: </form >
47 访问选中的Select
1: <form name=”myForm” >
2: <select name=”mySelect” >
3: <option value=”First Choice” >1 </option >
4: <option value=”Second Choice” >2 </option >
5: <option value=”Third Choice” >3 </option >
6: </select >
7: </form >
8: <a href= &amp;apos;# &amp;apos; onClick= &amp;apos;alert(document.myForm.mySelect.value); &amp;apos; >Check Selection List </a >
48 动态增加Select项
1: <form name=”myForm” >
2: <select name=”mySelect” >
3: <option value=”First Choice” >1 </option >
4: <option value=”Second Choice” >2 </option >
5: </select >
6: </form >
7: <script language=”JavaScript” >
8: document.myForm.mySelect.length++;
9: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].text = “3”;
10: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].value = “Third Choice”;
11: </script >
49 验证表单字段
1: <script language=”JavaScript” >
2: function checkField(field) {
3: if (field.value == “”) {
4: window.alert(“You must enter a value in the field”);
5: field.focus();
6: }
7: }
8: </script >
9: <form name=”myForm” action=”target.html” >
10: Text Field: <input type=”text” name=”myField”onBlur=”checkField(this)” >
11: <br > <input type=”submit” >
12: </form >
50 验证Select项
1: function checkList(selection) {
2: if (selection.length == 0) {
3: window.alert(“You must make a selection from the list.”);
4: return false;
5: }
6: return true;
7: }
还是先继续写完JS就这么回事系列吧～
43 表单构成
1: <form method=”post” action=”target.html” name=”thisForm” >
2: <input type=”text” name=”myText” >
3: <select name=”mySelect” >
4: <option value=”1” >First Choice </option >
5: <option value=”2” >Second Choice </option >
6: </select >
7: <br >
8: <input type=”submit” value=”Submit Me” >
9: </form >
44 访问表单中的文本框内容
1: <form name=”myForm” >
2: <input type=”text” name=”myText” >
3: </form >
4: <a href= &amp;apos;# &amp;apos; onClick= &amp;apos;window.alert(document.myForm.myText.value); &amp;apos; >Check Text Field </a >
45 动态复制文本框内容
1: <form name=”myForm” >
2: Enter some Text: <input type=”text” name=”myText” > <br >
3: Copy Text: <input type=”text” name=”copyText” >
4: </form >
5: <a href=”#” onClick=”document.myForm.copyText.value =
6: document.myForm.myText.value;” >Copy Text Field </a >
46 侦测文本框的变化
1: <form name=”myForm” >
2: Enter some Text: <input type=”text” name=”myText” onChange=”alert(this.value);” >
3: </form >
47 访问选中的Select
1: <form name=”myForm” >
2: <select name=”mySelect” >
3: <option value=”First Choice” >1 </option >
4: <option value=”Second Choice” >2 </option >
5: <option value=”Third Choice” >3 </option >
6: </select >
7: </form >
8: <a href= &amp;apos;# &amp;apos; onClick= &amp;apos;alert(document.myForm.mySelect.value); &amp;apos; >Check Selection List </a >
48 动态增加Select项
1: <form name=”myForm” >
2: <select name=”mySelect” >
3: <option value=”First Choice” >1 </option >
4: <option value=”Second Choice” >2 </option >
5: </select >
6: </form >
7: <script language=”JavaScript” >
8: document.myForm.mySelect.length++;
9: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].text = “3”;
10: document.myForm.mySelect.options[document.myForm.mySelect.length - 1].value = “Third Choice”;
11: </script >
49 验证表单字段
1: <script language=”JavaScript” >
2: function checkField(field) {
3: if (field.value == “”) {
4: window.alert(“You must enter a value in the field”);
5: field.focus();
6: }
7: }
8: </script >
9: <form name=”myForm” action=”target.html” >
10: Text Field: <input type=”text” name=”myField”onBlur=”checkField(this)” >
11: <br > <input type=”submit” >
12: </form >
50 验证Select项
1: function checkList(selection) {
2: if (selection.length == 0) {
3: window.alert(“You must make a selection from the list.”);
4: return false;
5: }
6: return true;
7: }