JS下拉选择框与输入框联动实现选中值自动填充

<html>
<head>
<title>下拉选择框与输入框联动，直接添加选中值到输入框</title>
</head>
<body>
<select id="uiSel">
  <option value="-1">请选择</option>
  <option value="until1">unti1</option>
  <option value="until2">unti2</option>
  <option value="until3">unti3</option>
  <option value="until4">unti4</option>
  <option value="until5">unti5</option>
</select>
<input type="text" name="" id="show" />
</body>
<script type="text/javascript">
document.getElementById('uiSel').onchange=function (){
  if(this.options[0].value==-1)this.options[0]=null;
  document.getElementById('show').value=this.value
};
</script>
</html>