vue实现两个区域滚动条同步滚动

<div class="customer-span" ref="systemForm" @scroll="sysHandleScroll()" @mouseover="changeFlag(false)">
 <div class="customer-span-form">
 <el-form label-suffix=":" class="form-static" label-position="right" label- 
 width="100px">
  <el-form-item v-for="(item, index) in formItem" :key="index" :label="item.label">
  {{ systemFormData[item.model] }}
  </el-form-item>
 </el-form>
 </div>
</div>
<div class="customer-span" ref='externalForm' @scroll="exterHandleScroll()" @mouseover="changeFlag(true)">
 <div class="customer-span-form">
 <el-form label-suffix=":" class="form-static" label-position="right" label- 
 width="100px">
  <el-form-item v-for="(item, index) in formItem" :key="index" :label="item.label">
  {{ externalFormData[item.model] }}
  </el-form-item>
  </el-form>
 </div>
</div>

data() {
 return {
 flag: false
 }
},
method: {
 changeFlag(flag) {
 this.flag = flag
 },
 // 左右滚动条滚动同步
 sysHandleScroll() {
 if (!this.flag) {
  this.$refs.externalForm.scrollTop = this.$refs.systemForm.scrollTop
 }
 },
 exterHandleScroll() {
 if (this.flag) {
  this.$refs.systemForm.scrollTop = this.$refs.externalForm.scrollTop
 }
 }
}