怎么实现选择控件和textbox控件显示内容的互动?
多项选择 
 然后textbox控件里面的内容是根据多项选择里面的选择项动态生成的? 
 这样的功能   怎么用   javascript脚本来实现啊? 
------解决方案-------------------- <!DOCTYPE HTML PUBLIC  "-//W3C//DTD HTML 4.0 Transitional//EN ">  
  <HTML>  
  <HEAD>  
  <TITLE>  New Document  </TITLE>  
  <META NAME= "Generator " CONTENT= "EditPlus ">  
  <META NAME= "Author " CONTENT= " ">  
  <META NAME= "Keywords " CONTENT= " ">  
  <META NAME= "Description " CONTENT= " ">  
  </HEAD>    
  <BODY>  
  <select onchange= "dd(this) ">  
  <option value= "1 "> 11 </option>  
  <option value= "2 "> 22 </option>  
  </select >  
  <input type= "text " name= "aa " id= "aa ">  
  <script>  
 function dd(a){ 
 if(a.value== "1 "){ 
 document.getElementById( "aa ").value= "11 " 
 } 
 if(a.value== "2 "){ 
 document.getElementById( "aa ").value= "22 " 
 } 
 } 
  </script>  
  </BODY>  
  </HTML>
------解决方案-------------------- <!DOCTYPE html PUBLIC  "-//W3C//DTD XHTML 1.0 Strict//EN "  "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd ">  
  <html xmlns= "http://www.w3.org/1999/xhtml ">  
  <head>  
  <meta http-equiv= "Content-Type " content= "text/html; charset=gb2312 " />  
  <title> test </title>  
  <script type= "text/javascript ">  
 function itemCheck() 
 { 
 	var ochkForm	= document.getElementById( 'resForm '); 
 	var oText 		= document.getElementById( 'content ');	 
 	var ochkBoxes	= ochkForm[ 'items[] ']; 
 	oText.value =  ' '; 
 	for(var i = 0 ; i <ochkBoxes.length; i++ ) 
 	{ 
 		if ( ochkBoxes[i].checked ) 
 			oText.value += ochkBoxes[i].value+ '  '; 
 	} 
 } 
  </script>  
  </head>  
  <body>  
  <form id= "resForm " name= "resForm " >  
  <textarea id= "content " name= "content ">  </textarea>  
  <br>  
  <input type= "checkbox " name= "items[] " value= "1 " onclick= "itemCheck() "> 选项1 <br/>  
  <input type= "checkbox " name= "items[] " value= "2 " onclick= "itemCheck() "> 选项2 <br/>  
  <input type= "checkbox " name= "items[] " value= "3 " onclick= "itemCheck() "> 选项3 <br/>  
  <input type= "checkbox " name= "items[] " value= "4 " onclick= "itemCheck() "> 选项4 <br/>  
  </form>  
  </body>    
  </html>  
------解决方案-------------------- <!DOCTYPE HTML PUBLIC  "-//W3C//DTD HTML 4.0 Transitional//EN ">  
  <HTML>  
  <HEAD>  
  <TITLE>  New Document  </TITLE>  
  <META NAME= "Generator " CONTENT= "EditPlus ">  
  <META NAME= "Author " CONTENT= " ">  
  <META NAME= "Keywords " CONTENT= " ">  
  <META NAME= "Description " CONTENT= " ">  
  </HEAD>    
  <BODY>  
  <select onchange= "dd(this) ">  
  <option v