this.$set的使用方法
//对象的属性sex的值更新为"男" let obj = {name:"六四",age:18,sex:"女"} this.$set(obj,"sex","男") //第一个参数是对象，第二个参数是更新的属性名称，第三个参数是新的内容 //更新之后的obj是 {name:"六四",age:18,sex:"男"}
let arr = ["星期一","星期二","星期日"] this.$set(arr,2,"星期三") //第一个参数是数组，第二个参数是下标索引，第三个参数是新的内容 //更新之后的arr是["星期一","星期二","星期三"]