仿淘宝商品详情大小图展示

preImg(){
  if (this.currentImgIndex === 0){
    this.currentImgIndex = this.imgList.length - 1
  } else {
    --this.currentImgIndex
  }
  let value = this.imgList[this.currentImgIndex]

  this.changeImg(value)
},
// 向右查看照片
addImg(){
  if (this.currentImgIndex === this.imgList.length - 1){
    this.currentImgIndex = 0
  } else {
    ++this.currentImgIndex
  }
  let value = this.imgList[this.currentImgIndex]

  this.changeImg(value)
},