js：
    $(function () {
$('.respP').children().length;
var paWidth = parseInt($('.respP').css('width'));
var childArr = document.getElementsByClassName('resp');
var childWidth = paWidth/($('.respP').children().length);
for(var i = 0;i< childArr.length;i++){
childArr[i].style.width = childWidth+'px';
  }
})


html:


<div class="respP" style="width: 300px;height: 20px">
<div class="resp">急急急</div>
<div class="resp">hjsjdjs</div>
</div>


css:


.resp{
  float: left;
  text-align: center;
 }