js 动态改变样式例子
请看代码：
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<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head> <title>用JS动态改变样式</title> <script language="javascript" type="text/javascript">function $(element) { if (typeof element == 'string') return document.getElementById(element);}//获取焦点时触发function questionOnFocus(obj){if (obj.value =='请输入您的问题！(限40字)'){$("ptitle").className = "my_font_color2";obj.value ='';}}//失去焦点时触发function questionOnBlur(obj){if(obj.value =='' || obj.value =='请输入您的问题！(限40字)'){$("ptitle").className= "my_font_color1";}else{$("ptitle").className = "my_font_color2"; } if(obj.value ==''){obj.value='请输入您的问题！(限40字)';}}//获取焦点时触发function descriptionOnFocus(obj){if (obj.value =='请描述您的问题！(限500字)'){$("pcontent").className = "my_font_color2";obj.value ='';}}//失去焦点时触发function descriptiOnBlur(obj){if (obj.value ==''){$("pcontent").className= "my_font_color1";obj.value='请描述您的问题！(限500字)';}else{$("pcontent").className = "my_font_color2"; }}</script><style>.my_font_color1{font-family:Arial, Helvetica, sans-serif;color:blue;}.my_font_color2{font-family:Arial, Helvetica, sans-serif;color:red;}</style> </head> <body> <center>标题：<input type="text" size="34" maxlength="40"id="ptitle" name="ptitle"value="请输入您的问题！(限40字)" name="pcontent" cols="37" rows="7"onBlur="descriptiOnBlur(this)"onFocus="descriptionOnFocus(this)"class="my_font_color1">请描述您的问题！(限500字)</textarea></center> </body></html>?上面就是简单的js改变样式的例子。
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