打印预览及打印

1. dom替换　　　　-- dom替换会导致事件失效，如果重新加载的话又会影响到体验；

2. 新窗口打印　　　-- 新窗口缺因为样式问题也不好解决，都不满足项目的需求;

printBillDig(){ //打印单据
      var printDiv = document.createElement(‘div‘);
      printDiv.innerHTML = this.$refs.itemList.innerHTML;
      printDiv.style.position = ‘fixed‘;
      printDiv.style.left = ‘0‘;
      printDiv.style.top = ‘0‘;
      printDiv.style.width = ‘100%‘;
      printDiv.style.height = ‘100%‘;
      printDiv.style.zIndex = ‘100000‘;
      printDiv.style.background = ‘#fff‘;
      printDiv.style.overflow = ‘auto‘;
      document.body.appendChild(printDiv);
      window.print();
      document.body.removeChild(printDiv);
},