http://www.runoob.com/w3cnote/vue2-start-coding.html
https://cn.vuejs.org/v2/guide/instance.html
https://segmentfault.com/q/1010000005790864/a-1020000005791335
http://www.runoob.com/w3cnote/vue2-start-coding.html
原文：https://www.cnblogs.com/chendeming/p/8300975.html