Understanding of computed Data in VUE: 1.com Puted monitors its own attributes, which are not declared in data but defined directly in computed, and calculates a new attribute through existing attributes (instance data placed under objects such as data). 2.com Puted relies on responsive data and is invoked only when the data changes. Puted attributes have two methods: Get and set. If the attribute value is a function, the default value is GET and a return value is required. Do not change the instance data of objects such as data in the set method. Otherwise, if the dependency data changes, computed will be invoked, leading to an infinite loop. As with computed, dependent data is triggered when it changes, but instead of caching, 2 is retriggered each time. Is a single property, a single object listener (the listener is the instance data declared in the data object) 3. Hanlder and deep can deeply listen to loop methods, which are different from computed and watch in that they do not rely on dependent data. The page is called once after it is loaded and only when it is called later