请问如何实现在select中当触发onchange事件的时候可以改变它旁边的text的value值？

Question

<select onchange="t1.value = this.options[this.selectedIndex].text">
<option>a</option>
<option>b</option>
</select>
<input type=text id=t1>

Answer 1

<select name=one></select>
<select name=two></select>
<select name=three></select>
<select name=four></select>
<input name=result><script>
var arrSel=["one","two","three","four"];//arrSel定义了要修改的下拉框
var i=0,arrData=[];//arrData中搁的是数据,每条都显示各级的数据
arrData[i++]=["2000","4","14","一点"]
arrData[i++]=["2000","4","14","二点"]
arrData[i++]=["2000","4","18","三点"]
arrData[i++]=["2000","7","14","二点"]
arrData[i++]=["2001","6","15","二点"]
arrData[i++]=["2001","6","23","七点"]
arrData[i++]=["2001","8","18","二点"]
arrData[i++]=["2002","7","1","二点"]
arrData[i++]=["2002","7","1","三点"]
arrData[i++]=["2002","7","11","二点"]
arrData[i++]=["2002","7","19","二点"]
</script>
<script>
function qswhInit(num){
/******* by qiushuiwuhen(2002-5-15) ********/
var i,j,arrTemp=[];
for(i=0;i<num;i++)arrTemp[i]=document.all(arrSel[i]).options[document.all(arrSel[i]).selectedIndex].text
if(num==arrSel.length){//这里处理最后的数据。
document.all("result").value="选中了("+arrTemp[0]+","+arrTemp[1]+","+arrTemp[2]+","+arrTemp[3]+")";return;
}
with(document.all(arrSel[num])){
length=0
for(i=0;i<arrData.length;i++){
for(j=0;j<num;j++)if(arrTemp[j]!=arrData[i][j])break;
if(j!=num)continue;
if(length==0||options[length-1].text!=arrData[i][num])
options[length++].text=arrData[i][num];
}
onchange=new Function("qswhInit("+(num+1)+")");
onchange();
}
}
qswhInit(0);//初始化
</script>
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Answer 2

<select name="ff" onchange="ck">
<option>123</option>
<option>456</option>
</select>
<script>
    function ck(){
        tt.value=ff.options[this.selectedIndex].text;
}
</script>
<input type=text name=tt>