JavaScript二级联动下拉菜单

< html >
< head >
< title >
test
</ title >
< script language = " javascript " >

// var select1_len = document.frm.s1.options.length;
var select2  =   new  Array( 4 );


for  (i = 0 ; i < 4 ; i ++ ) 
{
 select2[i] = new Array();
}
// 定义基本选项
select2[ 0 ][ 0 ]  =   new  Option( " 请选择 " ,  "   " );

select2[ 1 ][ 0 ]  =   new  Option( " PHP " ,  "   " );
select2[ 1 ][ 1 ]  =   new  Option( " ASP " ,  "   " );
select2[ 1 ][ 2 ]  =   new  Option( " JSP " ,  "   " );

select2[ 2 ][ 0 ]  =   new  Option( " C/C++ " ,  "   " );
select2[ 2 ][ 1 ]  =   new  Option( " Java " ,  "   " );
select2[ 2 ][ 2 ]  =   new  Option( " C# " ,  "   " );

select2[ 3 ][ 0 ]  =   new  Option( " Perl " ,  "   " );
select2[ 3 ][ 1 ]  =   new  Option( " Ruby " ,  "   " );
select2[ 3 ][ 2 ]  =   new  Option( " Python " ,  "   " );


function redirec(x)
{
 var temp = document.frm.s2; 
 for (i=0;i<select2[x].length;i++)
 {
  temp.options[i]=new Option(select2[x][i].text,select2[x][i].value);
 }
 temp.options[0].selected=true;

}
</ script >
</ head >
< body >
< form name = " frm " >
< select name = " s1 "  onChange = " redirec(this.options.selectedIndex) " >
  < option selected > 请选择 </ option >
  < option value = " 1 " > 脚本语言 </ option >
  < option value = " 2 " > 高级语言 </ option >
  < option value = " 3 " > 其他语言 </ option >
</ select >
< select name = " s2 " >
  < option value = " 请选择 "  selected > 请选择 </ option >
</ select >
</ form >
</ body >
</ html >