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JS fetch - data disappear or infinite loop

This function here has been causing me some trouble for a while.

When printing "res" it shows the object and its fields fine, however when outside of this loop data is then undefined, which is understandable considering the variable is only being initialized within the function.

However if I try to use the setData(field) or setServerUser(field) inside it executes recursively.

I thought the solution to this would be to call either setData(field) or setServerUser(field) outside the loop, though same result.

code:

    const [ serverUser, setServerUser ]=useState('')
    const [ data, setData ]=useState('')

    async function fetchProfile(){
        const res = await fetch(
            "http://XXX.XXX.XXX.XXX:8080/User/getByEmail", {
            method: "POST",  
            headers:{"Content-Type":"application/json"},
            body:JSON.stringify( { email : user.email }  ) } )

        const data = res.json().then((res) => {


            // V both of these causes infinite looping
            // V i dont think this is the right spot to set - but res doesnt exist outside
            //setServerUser(res)
            //setData(res)

            console.log(res) // < this actually prints the object perfectly
        });
        console.log(res) // < equal to undefined here

        // V both of these causes infinite looping
        // V this makes the most sense to me setting here but yet same result
        //setServerUser(data);
        //setData(data)

        console.log("data" + data) // < this returns data[object Promise]
    }

    fetchProfile();
about 4 years ago · Juan Pablo Isaza
1 answers
Answer question

0

Something to do with useEffect, useState and it overwriting eachother

 const [ serverUser, setServerUser ]=useState('')

//3. passing an empty array for on mount (when the page loads)
useEffect(() => {
    fetch("http://XXX.XXX.XXX:8080/User/getByEmail", {
        method: "POST",  
        headers:{"Content-Type":"application/json"},
        body:JSON.stringify( { email : user.email } )
    })
    .then(response => response.json())
    .then(json => { setServerUser(json) })
},[]) 
about 4 years ago · Juan Pablo Isaza Report
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