前端打印功能

转载大神总结

https://www.cnblogs.com/potatog/p/7412905.html

https://www.cnblogs.com/xuange306/p/5615885.html

https://www.cnblogs.com/laiweidong/archive/2013/01/09/2852562.html

http://www.360doc.com/content/13/0306/14/10504424_269660278.shtml