Component is one of the most powerful functions of vue.js, and the scope of component instances is independent of each other, which means that data between different components cannot be referenced to each other. For Vue, message passing between components is very important. Vue component flow chart summarizes several communication modes between Vue components, such as props, $emit / $on, vuex, $parent / $children, $attrs / $listeners and provide / inject, and describes the differences and usage scenarios