Javascript动态改变imputtype属性

<script type="text/javascript">
 function shoppw(thebox){
 var ps = document.getElementById('ps');
 var pass = document.getElementById('pass');
 ps.removeChild(pass);
 var psImput = document.createElement("INPUT");
 
 if(pass.type == 'password'){
 psImput.type = "text";
 } else {
 psImput.type = 'password';
 }
 psImput.id = 'pass';
 psImput.name = "password";
 psImput.maxlength="15";
 ps.appendChild(psImput);
 }
</script>

<td class="label"> * <label for="password" accesskey="">登录密码：</label></td>
 <td ><div id="ps"><input type="text" name="password" maxlength="15" id="pass" /></div>
 <input name="checkbox2" type="checkbox" value="true" checked="checked" id="show" onclick="shoppw(this)" />
 <label for="show" accesskey="">显示</label></td>