The difference between v-if and v-show? And how to choose

Straightforward:The initialization of v-if is fast, but the switching cost is high; the initialization of v-show is slow. But the switching cost is low

a. Common points

Are dynamically displaying DOM elements

b. Difference

i: Different implementation methods

 v-if是动态的向DOM树内添加或者删除DOM元素；
 v-show是通过设置DOM元素的display样式属性控制显示或者隐藏；

ii: The compilation process is different

v-if切换有一个局部编译/卸载的过程，切换过程中合适地销毁和重建内部的事件监听和子组件；
v-show只是简单的基于css切换；

iii: Different compilation conditions

v-if是惰性的，如果初始条件为假，则什么也不做；只有在条件第一次变为真时才开始局部编译（编译被缓存？
编译被缓存后，然后再切换的时候进行局部卸载); 
v-show是在任何条件下（首次条件是否为真）都被编译，然后被缓存，而且DOM元素保留；

iiii: Different performance consumption

 v-if有更高的切换消耗；
 v-show有更高的初始渲染消耗

C. Usage scenarios

v-if is suitable for operating conditions that are unlikely to change, or changes are not very frequent.
v-show is suitable for frequent switching.