Uncaught Error: Too many re-renders. React limits the number of renders to prevent an infinite loop-CodePudding

I am attempting to create a ProtectedRoutes component, however, I seem to have created an infinite loop somewhere that I can't seem to figure out. I'm a beginner.

It should check if there is a cookie stored, and if so, go to the component. If not, it should navigate back to the main page.

ProtectedRoutes.js

import React, { Component, useState } from "react";
import { Route, Navigate } from "react-router-dom";
import Cookies from "universal-cookie";
const cookies = new Cookies();


export default function ProtectedRoutes({component: Component, ...rest}) {
    const [auth, setAuth] = useState(false);
    //get cookie from browser if logged in
    const token = cookies.get("TOKEN");
    if (token) {
        setAuth(true);
    };
    
    return auth ? <Component /> : <Navigate to="/" />
}

App.js

import { Container, Col, Row } from "react-bootstrap";
import "./App.css";
import Register from "./Register";
import Login from "./Login";
import { Routes, Route } from "react-router-dom";
import Account from "./Account";
import FreeComponent from "./FreeComponent";
import AuthComponent from "./AuthComponent";
import Private from "./ProtectedRoutes";
import ProtectedRoutes from "./ProtectedRoutes";

function App() {
  return (
    <Container>
      <Row>
        <Col className="text-center">
          <h1 className="header">React Authentication Tutorial</h1>

          <section id="navigation">
            <a href="/">Home</a>
            <a href="/free">Free Component</a>
            <a href="/auth">Auth Component</a>
          </section>
        </Col>
      </Row>
      
      {/* Routes */ }
      <Routes>
        <Route exact path="/" element={ <Account /> } />
        <Route exact path="/free" element={ <FreeComponent /> } />
        <Route path="/auth" element={<ProtectedRoutes component={AuthComponent} />} />
      </Routes>
    </Container>
  );
}

export default App;

AuthComponent.js

import React from 'react';

export default function AuthComponent() {
    return (
        <div>
            <h1 className="text-center">Auth Component</h1>
        </div>
    );
}

CodePudding user response：

Yow problem Is heaw.


export default function ProtectedRoutes({component: Component, ...rest}) {
    const [auth, setAuth] = useState(false);
    //get cookie from browser if logged in
    const token = cookies.get("TOKEN");
    if (token) {
        setAuth(true);
    };
    
    return auth ? <Component /> : <Navigate to="/" />
}

You need yo put setAuth in a useEffect


export default function ProtectedRoutes({component: Component, ...rest}) {
    const [auth, setAuth] = useState(false);
    //get cookie from browser if logged in
    const token = cookies.get("TOKEN");
   React.useEffect(()=>{
    if (token) {
        setAuth(true);
    }
},[token]);
    
    return auth ? <Component /> : <Navigate to="/" />
}

CodePudding user response：

In ProtectedRoutes component, you're setting a state (setAuth in this case) directly inside the component, this is what happens when you do that:

React re-renders a component every time a state change is detected thus when you wrote

export default function ProtectedRoutes({component: Component, ...rest}) {
    ...
    if (token) {
        setAuth(true);
    };
    ...
}

you're running setAuth(sets a new state true) every time the component renders(re-renders) and in turn, re-rendering the component every time because of the state change which is why have an infinite loop there. , this works like this:

It runs everytime a dependency changes(passed as an array), and when you pass an empty array it runs just twice - when the component mounts(renders the first time) and when it unmounts.

What you need to do is to pass an empty array as a dependency as below

import { useEffect } from 'react'

export default function ProtectedRoutes({component: Component, ...rest}) {
    ...
    useEffect(() => {
        if (token) {
            setAuth(true);
        };
    }, [])   
    ...
}

this setAuth just once when the component mounts