wxml：

<view class="fromItem">
        <view class="fromLable">退货单号</view>
        <view class="fromValues">{{orderDetail.returnNo}}<view class="copy" bindtap="copyText" data-key="{{orderDetail.returnNo}}">复制</view></view>
      </view>

js：

copyText(e) { // 复制订单编号
    console.log('e',e)
    let key = e.currentTarget.dataset.key;
    wx.setClipboardData({
      data: key,
      success(res) {
        wx.getClipboardData({
          success(res) {
            wx.showToast({
              title: '复制成功',
            })
          }
        })
      }
    })
  },