Getting value of input causing flickering in React

Question

I am attempting to track the value of two login input fields by getting their value on change and storing this value in the local state so that when the user submits the login, I can just get the current values from the state. However, this results in the inputs flickering when I type text into them and also a weird glitch when I type in the password field (the cursor jumps back to the email field). The glitch can be observed below (note, I am not shift-tabbing back to the email field, it seems to be happening automatically for some reason when I type in the password field).

The following is the code for my profile_tile.js which I have as a component nested within a navbar:

import React, { useState } from 'react'
import { useFirebase, isLoaded, isEmpty } from 'react-redux-firebase'
import { useSelector } from 'react-redux'
import Modal from '../../modal'

export default function ProfileTile() {
    const firebase = useFirebase()
    const auth = useSelector(state => state.firebase.auth)
    const profile = useSelector(state => state.firebase.profile)

    const [showLoginModal, setLoginModalShow] = useState(false)
    const [showSignupModal, setSignupModalShow] = useState(false)

    const [email, setEmail] = useState('')
    const [password, setPassword] = useState('')

    const createNewUser = () => {
        firebase.createUser({ email, password })
        setLoginModalShow(false)
        setSignupModalShow(false)
    }

    const handleEmailChange = event => {
        setEmail(event.target.value)
        console.log('EMAIL' + event.target.value)
    }

    const handlePasswordChange = event => {
        setPassword(event.target.value)
        console.log('PASSWORD' + event.target.value)
    }

    const logout = () => {
        firebase.logout()
    }

    const handleLoginModalShow = () => {
        setLoginModalShow(true)
        setSignupModalShow(false)
    }

    const handleLoginModalHide = () => {
        setLoginModalShow(false)
    }

    const handleSignupModalShow = () => {
        setLoginModalShow(false)
        setSignupModalShow(true)
    }

    const handleSignupModalHide = () => {
        setSignupModalShow(false)
    }

    const handleLogin = () => {
        firebase.login({ email: email, password: password })
        setLoginModalShow(false)
        setSignupModalShow(false)
    }

    const loginModal = showLoginModal ? (
        
            
                
                    
                        
                        
                            
                                
                                    
                                        
                                    
                                    
                                         setPassword(event.target.value)}
                                        />
                                    
                                    
                                        Sign In
                                    
                                
                                
                                    
                                        Forgot your password?
                                    
                                
                                
                                
                                    Don't have an account?
                                    
                                        Sign Up
                                    
                                
                            
                        
                    
                
            
        
    ) : null

    const signupModal = showSignupModal ? (
        
            
                
                    
                        
                        
                            
                                
                                    
                                        
                                    
                                    
                                        
                                    
                                    
                                        Sign Up
                                    
                                
                            
                        
                    
                
            
        
    ) : null

    return (
        
            
                {!isLoaded(auth) ? (
                    
                        loading
                    
                ) : isEmpty(auth) ? (
                    
                        Log In
                    
                ) : (
                    
                        
                            {profile.email}
                        
                        
                            Log Out
                        
                    
                )}
            
            {loginModal}
            {signupModal}
        
    )
}

My modal.js component is as follows:

import React, { useState, useEffect } from 'react'
import ReactDOM from 'react-dom'
import './style.css'

const modalRoot = document.getElementById('modal-root')
const modalElement = document.createElement('div')

export default function Modal(props) {
    useEffect(() => {
        modalRoot.appendChild(modalElement)
        return () => {
            modalRoot.removeChild(modalElement)
        }
    })
    return ReactDOM.createPortal(props.children, modalElement)
}

My inputs are situated within a modal component which I display as an overlay using a portal. I have gone through related questions and tried using other methods but nothing seems to work. I appreciate any help!

Drew Reese · Accepted Answer

Your useEffect hook doesn't have a dependency array which will run on every render. You likely meant to append a child once when mounting so try an empty dependency array.

export default function Modal(props) {
    useEffect(() => {
        modalRoot.appendChild(modalElement)
        return () => {
            modalRoot.removeChild(modalElement)
        }
    }, []); // Empty dependency array to run once "on mount"

    return ReactDOM.createPortal(props.children, modalElement);
}

Getting value of input causing flickering in React

Answers (1)

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