为什么试了不行呢
window.onload=function(){
var oDiv=document.getElementById('div1');
var oIpt=document.getElementById('ipt1');
oIpt.onfocus=function(){
oDiv.style.className='form-group has-error';
}
}
<div class="container" style="
margin-top: 100px;">
<form>
<div class="form-group" id="div1" style="width:45%">
<input type="text" id="ipt1" class="form-control" id="name"
placeholder="请输入用户名">
</div>
</form>
</div>
oDiv.classList.add('has-error')
oDiv.className='form-group has-error';