1. The properties whose names start with $ are the properties provided internally
2. Reasons why event modifiers are used: methods only have pure data logic, rather than dealing with DOM event details
3. If the value of v-if is false, the element does not exist on the page; if the value is true, it is displayed on the page.
v-show If the value is false, the element hides display: none; if the value is true, the element displays display: block
Frequent operation of dom display and hiding, it is recommended to use v-show
initial page without a certain element, wait for a certain data to change, and then display a certain element, v-if
4. Although watch can be monitored, it is only shallow monitoring, only the first or second layer of data is monitored. If it is an object, deep monitoring is required.
list:{ //Deep monitoring deep:true, handler(newValue){ console.log(newValue); } }