Accessing variable in render in Reactjs and nodejs

Question

I'm storing data fetched from mongodb through nodejs in a variable like this

axios.post('http://localhost:5000/Users/login',user)
    .then(res=>{
     Userdata=res.data.users
      console.log(Userdata)
      console.log(Userdata._id)
       
    })

But I'm unable to access the data in variable in render function here:

if(this.state.loggedin){
  
      return <Redirect to={`/UI/Navbar/Dashboard/${Userdata._id}`}/>
    }

it gives me this error:

TypeError: Cannot read property '_id' of undefined

`Userdata=res.data.users` will occur _after_ your render function runs. — Nick Parsons, Aug 06 '20 at 13:52
The if statement is used in render function but I can't access the data stored in Userdata when redirecting it — Faraz Anwer, Aug 06 '20 at 13:55
console.log(Userdata) shows the data stored in json form Userdata variable — Faraz Anwer, Aug 06 '20 at 13:56
Does this answer your question? [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — Kunal Mukherjee, Aug 06 '20 at 14:00

score 0 · Answer 1 · answered Aug 06 '20 at 13:59

0

Both chunks are asynchronous. It is better to wrap async data load with useEffect, explicitly set the state of some top-level component, and propagate logged in user with Context API down to other components.

answered Aug 06 '20 at 13:59

Alexander Alexandrov

1,254
5
15

score 0 · Answer 2 · answered Aug 06 '20 at 14:04

0

Your render function tries to create a component in spite of the data is noe fetched yet. Thats why it Userdata is undefined. Your Userdata must be a state, when axios has fired, use setState to change Userdata. While Userdata is fetching you have to render something like 'in process...'

answered Aug 06 '20 at 14:04

Tarukami

1,160
5
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what type of state the variable should be? – Faraz Anwer Aug 06 '20 at 14:16
I have tried setting the Userdata in a state but it still does not work – Faraz Anwer Aug 06 '20 at 14:26
Userdate must be the same type as what res.data.users returns. I assume it is an array, so you cn set initial state as an empty one []. As for it still does not work - the snippet you show is not enough to find the problem. – Tarukami Aug 06 '20 at 14:58

Accessing variable in render in Reactjs and nodejs

2 Answers2