uniApp 再下一页修改上一页的值

let pages = getCurrentPages();  //获取所有页面栈实例列表
				let nowPage = pages[ pages.length - 1];  //当前页页面实例
				let prevPage = pages[ pages.length - 2 ];  //上一页页面实例
				if(prevPage.$vm.info.SN != undefined){
					prevPage.$vm.info.SN = str;
				}
				if(prevPage.$vm.info.deviceSn != undefined){
					prevPage.$vm.info.deviceSn = str;
				}
				
				uni.navigateBack({
					delta:1
				})