判断文字超过2行添加展开按钮，未超过则不显示，溢出部分显示省略号

 overflow: hidden;
 text-overflow: ellipsis;
 display: -webkit-box;
 -webkit-line-clamp: 2;
 -webkit-box-orient: vertical;

<div class="review">
 孙燕姿导师评语：这位同学唱功基础扎实，转音和高低音的切换非常自然，整首歌曲感情饱满，非常不错。整首歌曲感情饱满，非常不错。整首歌曲感情饱满，非常不错。
</div>

<style>
.review{
  padding-top: .2rem;
  padding-bottom: .1rem;
  margin-left: .9rem;
  font-size: .32rem;
  color:#b85423;
  line-height: 1.5em;
  position: relative;
}
.ellipsis{
  overflow : hidden;
  text-overflow: ellipsis;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
}
.spread{
  padding-right: .2rem;
  position: absolute;
  bottom: .09rem;
  right:0;

}
.spread i{
  width: .2266rem;
  height:.2266rem;
  display: inline-block;
  vertical-align: middle;
  background-image: url(/cdn_img/plusSprite.png);
  background-repeat: no-repeat;
  background-size: .2266rem .72rem;
}
.spread i.plus{
  background-position: 0 0;
}
.spread i.reduce{
  background-position: 0 -0.4933rem;
}
</style>

$('.teacher-review').forEach(function(v,i){
  // 引入flexible.js 进行移动端适配 
  // 根据flexible 获取rem 即 window.rem
  if(v.clientHeight > (1.27*window.rem)){
    var el = document.createElement('span');
    el.innerHTML = '... <i class="plus"></i>点击展开';
    el.className = 'spread';
    // 由于每条评论相间背景
    el.style.backgroundColor = i%2 == 0 "reduce"></i>点击收起');
  }else{
    $this.addClass('ellipsis').find('span').html('... <i class="plus"></i>点击展开');
  }
})