如何在本机反应中有条件地检查 state 值（obj 值）

Question

I need to check state value conditionally, I fetch user data from firestore as follow

 const[userdata,setUserdata]=useState()

 const fetchCard = async()=>{
       // user
       const uRef = query(doc(db,'users',user.uid))
     await getDoc(uRef)
       .then((snapshot)=>{setUserdata(snapshot.data())})
       .catch((error)=>{
          alert(error)
      })

  console.log("here",userdata)
}

it get user data as objects

here Object {
  "age": "25",
  "displayName": "ghd",
  "gender": "female",
  "id": "E8R52y6dD8XI3shXhnhS9pVzUpe2",
  "interestIn": "male",
  "job": "gdh",
  "photo": "https://firebasestorage.googleapis.com/v0/b/match-me-now.appspot.com/o/images%2FE8R52y6dD8XI3shXhnhS9pVzUpe2%2FprofilePicture.jpeg?alt=media&token=9084cdcb-beb7-44d3-8ab9-98e193955e75",
  "timestamp": Object {
    "nanoseconds": 755000000,
    "seconds": 1639913879,
  },
}

but I need check this values conditionally when this value has no value, to handle error. because I will use this value in useEffect,

 useEffect(()=>{
     fetchCard()
  
   console.log("in effect",userdata.age)
    
     
    },[])
  

if there is no object value in fetchCard, this will cause error in useEffect when call value from useEffect. So I want to check userdata value has or not. if array value, just check with const newdata = userdata.length > 0? userdata: ["no"] const newdata = userdata.length > 0? userdata: ["no"]

but how can check this object values has or not? need help.

Answer 1

You can use Object.keys to check if your object is empty. You can check this link for more options.

useEffect(() => {
  if(userdata){
   if(Object.keys(userdata).length == 0){
     //if empty
     }else{
     //not emmpty
    }
   }
}, [userdata])