求助,下拉框用javascript控制按钮显示

Question

<select name="a" id="a" onchange="document.getElementById('Sub').style.visibility=this.value>2?'visible':'hidden';">
<option value="1">1</option>
option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<div id="sub" style="visibility: hidden;">
<input type="button" name="Submit" value="详细" nclick="location.href='/'>
</div>上面的行不行？第三个和第四个时,onclick="location.href='/'的值不一样，你就自己改改吧

Answer 1

<select name="a" id="a" onchange="test(this)">
<option value="1">1</option>
option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<input type="button" id="sub" name="Submit" value="详细" onclick="location.href='/' style="display:none">
<script>
function (obj){
    if ( this.selectedIndex > 2 ){
        var tmpObj = document.getElementById('Sub')
        tmpObj.style.display = "";
        if ( this.selectedIndex =3){
              tmpObj.onclick = "location.href=......"
        }
        else if( this.selectedIndex =4){
              tmpObj.onclick = "location.href=...."        }   }
}
</script>

Answer 2

<select name="a" id="a" onchange="test(this)">
<option value="1">1</option>
option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<input type="button" id="sub" name="Submit" value="详细" onclick="location.href='/' style="display:none">
<script>
function (obj){
    var tmpObj = document.getElementById('Sub')
    if ( this.selectedIndex > 2 ){
        
        tmpObj.style.display = "";
        if ( this.selectedIndex =3){
              tmpObj.onclick = "location.href=......"
        }
        else if( this.selectedIndex =4){
              tmpObj.onclick = "location.href=...."        }    }
    else{
       tmpObj.style.display = "none";
    }
}
</script>

Answer 3

<select name="a" id="a" onchange="form.Submit.style.display=this.selectedIndex>1?'':'none'">
<option value="1">1</option>
option value="2">2</option>
<option value="3">3</option>
<option value="4">4</option>
</select>
<input type="button" name="Submit" value="详细" onclick="location.href='/'" style="display:none">