vue & $data & data
vm.a
===vm.$data.a
https://vuejs.org/v2/api/#data
https://flaviocopes.com/vue-data-function/
https://www.reddit.com/r/Vue/comments/4aw6nu/vue_data_usage/
vm.a
===vm.$data.a
https://vuejs.org/v2/api/#data
https://flaviocopes.com/vue-data-function/
https://www.reddit.com/r/Vue/comments/4aw6nu/vue_data_usage/