Lost input focus on hooks function state change

Question

When i define the hooks state in the parent function i lost input field focus on first key press. I need the state definition in the root function.

import React, { useState } from 'react'

function Test1(props) {
    const [test, setTest] = useState({value1: "", value2:""});

    const Test = () => {

        const handleChange= (e) => {
            const _test = {...test, [e.target.name]: e.target.value}
            setTest(_test)
        }

        return (
            <div style={{ margin: "200px" }}>
                <input name="value1" value={test["value1"]} onChange={handleChange}></input>
                <input name="value2" value={test["value2"]} onChange={handleChange}></input>
                <button onClick={() => console.log(test)}>Console.Log</button>
            </div>
        )
    }


    return (
        <Test />
    );

}


export default Test1;

But if I move the state definition in to the child function it works.


import React, { useState } from 'react'

function Test1(props) {

    const Test = () => {
        const [test, setTest] = useState({value1: "", value2:""});

        const handleChange= (e) => {
            const _test = {...test, [e.target.name]: e.target.value}
            setTest(_test)
        }

        return (
            <div style={{ margin: "200px" }}>
                <input name="value1" value={test["value1"]} onChange={handleChange}></input>
                <input name="value2" value={test["value2"]} onChange={handleChange}></input>
                <button onClick={() => console.log(test)}>Console.Log</button>
            </div>
        )
    }


    return (
        <Test />
    );

}


export default Test1;

So! Why is this happening and how can I get over it?

Can someone explain why one works and other does not? – ed22 Jun 06 '21 at 14:06 — ed22, Jun 06 '21 at 14:06

score 16 · Accepted Answer · answered Apr 12 '19 at 14:21

16

I have been seeing this pattern a lot where people nest components in methods in components. It may be an opinion, but I feel like this may not be a great pattern.

I would abstract the one component function and pass the props down to the 2nd. something like this

const Test = ({test, setTest}) => {

  const handleChange= (e) => {
      const _test = {...test, [e.target.name]: e.target.value}
      setTest(_test)
  }

  return (
      <div style={{ margin: "200px" }}>
          <input name="value1" value={test["value1"]} onChange={handleChange}></input>
          <input name="value2" value={test["value2"]} onChange={handleChange}></input>
          <button onClick={() => console.log(test)}>Console.Log</button>
      </div>
  )
}

function Test1(props) {
    const [test, setTest] = useState({value1: "", value2:""});


    return (
        <Test test={test} setTest={setTest} />
    );

}


export default Test1;

answered Apr 12 '19 at 14:21

Beaulne

529
4
9

Thank you Beualne. This approach solves the problem. – Unsal Apr 12 '19 at 14:34
One more question: If i have too many sub components, it's not feel good the abstract them all with props pass. this is where states advantages comes on, am i wrong? – Unsal Apr 12 '19 at 15:34
1

this does not work for me... I have the same problem – otto Jun 29 '20 at 07:58
I have the same problem with nested components. That's not work for me – Le Quang Jun 05 '21 at 15:42
1

This approach solves the problem for me as well, but is there a justification why it does not work the other way – mohantyArpit Jul 26 '21 at 15:39

Lost input focus on hooks function state change

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