Less 内容

.clearfix() {
    zoom: 1;
    &:before,
    &:after {
        content: "";
        display: table;
    }
    &:after {
        clear: both;
        visibility: hidden;
        font-size: 0;
        height: 0;
    }
}
.clearfix {
    .clearfix()
}

css内容

.clearfix {
  zoom: 1;
}
.clearfix:before,
.clearfix:after {
  content: "";
  display: table;
}
.clearfix:after {
  clear: both;
  visibility: hidden;
  font-size: 0;
  height: 0;
}