vue2 data 一定要是函数吗？

答：不一定，可以是对象，vue文档中表述有误导性而已，他自己的例子里也有对象的形式

---

function initData(vm){

  let data = vm.$options.data

  data = vm._data = typeof data === ‘function’ ? getData(data, vm) : data || {}
   /*

     Because here，data is a reference from vm.$options.data， 
     if data is an object, 
     when there are many instances of this Component,
     they all use the same `data`


      if data is a function, Vue will use method getData( a wrapper to executing data function, adds some error handling)

      and return a new object, this object just belongs to current vm you are initializing

    */

   ……


  // observing data
  observe(data, true)

}

内容来自：https://stackoverflow.com/a/61184547/17160403