JavaScript Basic Questions and Answers 4_Basic Knowledge
二、导航功能增强
1. 下拉菜单中的链接（Links in Select Menu）
Q：我如何实现在下拉菜单中链接到不同的页面？
A：要创建一个所示的下拉菜单：
你可以使用下面的代码：
- <form>
- <select
- onChange="if(this.selectedIndex!=0)
- self.location=this.options[this.selectedIndex].value">
- <option value="" selected>Select a page
- <option value="startpag.htm">JavaScript FAQ
- <option value="numbers.htm">Numbers
- <option value="strings.htm">Strings
- <option value="navigati.htm">Navigation
- <option value="colors.htm">Colors
- <option value="http://www.javascripter.net">JavaScripter.net
- select>
- form>
只需要把菜单项及其相应的URL改为你需要就可以了。你可以使用绝对地址（就像http://www.javascripter.net），也可以使用相对地址（像 mypage.htm）。
2. 按钮链接（Button Links）
Q：我怎么才能把一个按钮变为指向另外一个页面的超链接呢？
A：要创建一个按钮就像一个：
你可以使用这段代码：
- <form>
- <input type=button
- value="insert button text here"
- onClick="self.location='Your_URL_here.htm'">
- form>
只需要改为你需要的按钮文本和目标地址。试一下这个：
你可以使用绝对地址（像http://www.javascripter.net）也可以使用相对地址（像mypage.htm）。
3. 后退按钮（Back Button）
Q：我能让按钮像浏览器的“后退”按钮一样吗？
A：要创建你自己的后退按钮，可以使用这段代码：
- <form>
- <input type=button value="Back"
- onCLick="history.back()">
- form>
现在试一下：
4. 前进按钮（Forward Button）
Q：我能让按钮像浏览器中的“前进”按钮一样吗？
A：要创建自己的“前进”按钮，使用这段代码：
- <form>
- <input type=button value="Forward"
- onCLick="history.forward()">
- form>
如果浏览器上的前进按钮当前不可用，那么这个“前进”按钮同样不能工作。这种情况就是当前页是你浏览历史中的最后一页。换句话说，如果你是使用浏览器的“后退”按钮到达的这个页面（或者脚本编写的后退按钮），那么这个前进按钮就可以工作。现在试一下吧！
5. 查询字符串（Query Stirngs）
Q：我的脚步可以访问当前URL中的查询字符串吗？
A：查询字符串（或搜索字符串）是URL中的一个可选部分，它跟在文件名后面，以问号引导（?）。例如，下面的URL在HTML文件名后包含了一个查询字符串 ?myquery：
http://www.myfirm.com/file.html?myquery
你的脚本可以使用JavaScript的location.search属性访问当前URL中的查询字符按。点击下面按钮试一下看看！（为了查看地址中的URL，你可能想要在顶层浏览器窗口中显示这个页面。）
创建这些按钮的代码是：
- <form>
- <input type=button value="Add query ?test"
- onClick="selfself.location=
- self.location.protocol+'//'
- +self.location.host
- +self.location.pathname+'?test'">
- <input type=button value="Show query"
- onClick="alert('Query string: '+self.location.search)">
- <input type=button value="Remove query"
- onClick="selfself.location=
- self.location.protocol+'//'
- +self.location.host
- +self.location.pathname">
- form>
注意：查询字符串有时候可能不会如预期一样的工作。例如，如果你将这个页面保存本地磁盘上，上面在Internet Explorer 4.x就不会工作（但是在Netscape Navigator中依然有效）。
6. 向页面传递参数（Passing parameters to a page）
Q：我可以从也页面向另外一个页面传递参数吗？
A：可以。有几种不同的方式可以实现：
这里是一个简单的例子来演示所有这些传递参数的方法。传递的值应该是字符换“It_worked”。当你点击下面的按钮时，按钮的事件脚本会存在这些值（1）在名为parm_value的cookie中，（2）以顶层变量top.parm_value保存以及（3）在top.name属性中。然后，脚本引导浏览器到parm_get.htm，它的URL包含一个值为URL编码的查询字符串。
7. 查找文本（Searching for text）
Q：我怎样在页面查询一个特定的文本字符串？
A：在Netscape Navigator 4.x中，可以使用window.find(string) 方法查找；参见查找对话框。在Internet Explorer 4.x或更新版本中，创建一个文本范围对象（下面的例子中是TRang），然后使用TRang.findText(string)。
示例：下面的脚本根据用户输入的文本查找并在页面上高亮显示。
这个示例的代码为：
- <form name="f1" action=""
- onSubmit="if(this.t1.value!=null && this.t1.value!='')
- findString(this.t1.value);return false"
- >
- <input type="text" name=t1 value="" size=20>
- <input type="submit" name=b1 value="Find">
- form>
- <script language="JavaScript">
-
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