编辑代码

const updateDotAttr  = (obj,dot,data)=>{
    let dots = dot.split(".")
    dots.reduce((pre,cur)=>{
      console.log("pre=",pre,"cur=",cur,"pre[cur]=",pre[cur],"data=",data)
      pre[cur]=data
      return pre[cur]
    },obj)
}

const obj = {"a":{"b":{"c":{"d":1}}}}

updateDotAttr(obj,"a.b.c",{"d":2})
console.log("obj",obj)